Recently, there has been a bit of activity in GSC's lower tiers, with GSC NU being the rotational ladder spotlight and having some of its first analyses written, GSC UU being included in the UUPL, and GSC PU being created. Although GSC is a very old generation, it is only fairly recently in comparison that GSC NU came into existence (~2012/13). It was created by a bunch of GSC specialists over at Mount Silver, primarily Crystal_ and Jorgen. It was then subsequently adopted by PO and Smogon.
Now that GSC UU has gained exposure from UUPL, a more official viability ranking thread has been created, and the creation of GSC PU based on the (antiquated) Viability Rankings in the GSC NU forum as well as tiering debates about what should be included in PU have now also brought attention to the fact that GSC NU was created fairly arbitrarily. At the point that GSC NU was created, I would say that the GSC UU metagame was much less developed than it is now, and I think there are some Pokemon that should have made the cutoff for NU that remained UU. Ellicrum has helpfully provided a list of Pokemon that are listed as UU but not included on the viability ranking list, despite numerous NU Pokemon being included (a couple even being in A- and B).
Disjunction who seems to lead GSC NU in the NU forums has not logged in for a while, and our friendly RoA moderator Jellicent has no objections to discussion of potential tiering changes, so below are the candidates and how I perceive them to fare in the relevant metagames. I will be converting my personal NU viability rankings into the S/A/B/C/D system and comparing those against the UU viability rankings, rather than using the rankings in the NU forum.
Pokemon ranked B or above in both tiers
Pikachu
UU: B, NU: A
Pikachu is obviously very powerful, hitting about as hard as Zapdos. In UU, which is a relatively slow tier with lots of bulky hard-hitters, several of which are Water-types, Pikachu's strengths can shine, which enables it to achieve as high as B rank in GSC UU. In NU, where a lot of Pokemon are faster than Pikachu and two of the best Pokemon in the tier outmatch it, it comes in at A. The NU metagame has evolved around Pikachu, which has led to the rise of Dugtrio and other Pokemon that are faster, which has in turn caused Pikachu to sometimes turn into more of a liability than a useful Pokemon - one would often rather have a Pokemon they can actually switch into attacks, and stall teams tend to have it well covered. That said, its effect on the metagame should not be understated, and teams that are underprepared for it can easily be put into very dicey situations against it.
Mr. Mime
UU: A-, NU: A+
Mr. Mime is a Pokemon that brings a lot of utility to the table, with a multitude of possible sets available to it. It has a solid 100 base SpA, and the Pokemon that can wall its attacks in UU can do little about it spreading status or Baton Passing boosts to another Pokemon. In NU, Mr. Mime is clearly one of the strongest Pokemon in the tier, with very few viable Pokemon able to reliably handle it outside of itself. Psychic resists other than Mr. Mime are few and far between, and those that do resist it are mostly demolished by Thunderbolt. However, it does have a very low Defense stat, which can make it difficult to find an opportunity to come in without taking a lot of damage, except against itself. Additionally, it runs the risk of facing Thunder Wave or Shadow Ball Mr. Mime, both of which will make it even more susceptible to other threats. That said, a Pokemon whose best counter is itself does not tend to make for a healthy addition to a tier, so it was arguably a mistake to include Mr. Mime in the first place.
Haunter
UU: A-, NU: A-
I am not sure Haunter deserves such a high rank in the UU viability rankings. I'm presuming it is because of how powerful Granbull is as well as its access to Hypnosis and Explosion and coverage moves that are super effective against the tier's strongest Pokemon. Looking at the UUPL cumulative stats, it had a 37.5% win rate and was used 8 times. In GSC NU, it is quite useful because of its Shadow Ball hitting Mr. Mime hard while also being faster, and the normal and poison immunities are handy against Normal-types and Shuckle. However, Dugtrio switches into it relatively freely if it doesn't get caught by Hypnosis, and it is quite fragile. It can also have 4MS with Explosion/SBall/Tbolt/Psychic/Hypnosis, all of which are highly useful to pose a threat to relevant top tier Pokemon. The NU tier does not have any significant issues handling Haunter.
Unranked UU Pokemon that are currently banned from NU
Omastar
This Pokemon has very high SpA and is probably viable in UU. In theory, it should be able to come into a Granbull and dish out damage to anything that comes in, especially with Spikes up. However, unfortunately its typing and HP/SpD stats don't allow it to switch into much other than Normal-types.
Omastar Surf vs. Granbull: 156-184 (40.7 - 48%) -- guaranteed 3HKO after Leftovers recovery
Omastar Surf vs. Nidoqueen: 251-296 (65.5 - 77.2%) -- guaranteed 2HKO after Leftovers recovery
Omastar Hidden Power Electric vs. Slowbro: 131-154 (33.3 - 39.1%) -- guaranteed 3HKO after Spikes and Leftovers recovery
Omastar Surf vs. Ampharos: 122-144 (31.8 - 37.5%) -- 93.4% chance to 3HKO after Spikes and Leftovers recovery
In NU, I am pretty sure it would smack pretty much everything around while also resisting the STAB attacks of the many powerful Normal types (unlike Octillery/Dewgong). There is no way this thing fits in the current tier.
Omastar Hidden Power Grass vs. Octillery: 134-158 (37.9 - 44.7%) -- guaranteed 3HKO after Spikes and Leftovers recovery
Omastar Surf vs. Mr. Mime: 100-118 (35.3 - 41.6%) -- guaranteed 3HKO after Spikes and Leftovers recovery
Omastar Surf vs. Lickitung: 136-160 (35.5 - 41.7%) -- guaranteed 3HKO after Spikes and Leftovers recovery
Omastar Hidden Power Grass vs. Dewgong: 115-136 (30 - 35.5%) -- 31.4% chance to 3HKO after Spikes and Leftovers recovery
Hitmonlee
Hitmonlee is basically like Hitmonchan, which is a solid and balanced NU Pokemon, but with a much better stat distribution (Hitmonchan has 26 higher base Def, from which 15 went into Attack and the other 11 went into Speed for Hitmonlee). Importantly, Hitmonlee is no less bulky on the Special side. Hitmonlee also has access to Meditate which allows it to boost its own attack without sacrificing its Speed. Fighting is not a particular good type in UU, with a lot of the strongest Pokemon resisting it, and Hitmonlee does not learn Earthquake for Nidoqueen, nor does its Reversal set particularly scare Slowbro. In NU, even with its higher speed, it would still be slower than many common Pokemon in the metagame. However, while Mr. Mime is not too scared of switching into Hitmonchan once (even if it ends up tanking HP Ghost), Hitmonlee's attacks are more punishing:
Hitmonchan Hidden Power Ghost vs. Mr. Mime: 137-162 (48.4 - 57.2%) -- 47.7% chance to 2HKO after Leftovers recovery
Hitmonchan High Jump Kick vs. Octillery: 114-135 (32.2 - 38.2%) -- 0.9% chance to 3HKO after Leftovers recovery
Hitmonlee Hidden Power Ghost vs. Mr. Mime: 149-176 (52.6 - 62.1%) -- 99.8% chance to 2HKO after Leftovers recovery
Hitmonlee High Jump Kick vs. Octillery: 125-147 (35.4 - 41.6%) -- 80.8% chance to 3HKO after Leftovers recovery
It could be argued that this is a good thing, since it will encourage more people to use Xatu instead of Mr. Mime. I think it is hard to tell if Hitmonlee would be too strong for GSC NU at this point.
Dugtrio Earthquake vs. Hitmonlee: 136-160 (44.8 - 52.8%) -- 86.5% chance to 2HKO after Spikes and Leftovers recovery
Raichu
Raichu is fast and has a pretty solid SpA stat, plus access to Surf. This should in theory allow it to do decent damage to Nidoqueen while dominating Slowking, which is a highly desirable trait in GSC UU. However, its defenses are lacking and it only manages 41.9 - 49.3% against Nidoqueen with Surf, while Nidoqueen almost OHKOs in return with Earthquake. Teams with Ampharos or Hypno essentially wall it permanently, and there are not many Pokemon it can switch into safely. It is not hard to imagine why it does not see a lot of use and has not been listed on the viability rankings.
Raichu obviously does significantly less damage than Pikachu does, so should not be as threatening in GSC NU. However, it is also significantly harder to take down than Pikachu, living an Earthquake from Dugtrio while 2HKOing it with Surf, and being 3HKOed instead of 2HKOed by Mr. Mime, albeit having to rely on Thunder for a chance at 3HKOing in return. It would have plenty of defensive counter options, and would not be able to touch Grass-types if it chooses to use a Restalk set with Surf. It would also potentially make a good Pikachu counter. I would say it would be quite strong in the tier, but it is not clear if it would be overpowered.
Octillery Surf vs. Raichu: 125-147 (38.6 - 45.5%) -- guaranteed 3HKO after Leftovers recovery
Raichu Thunder vs. Octillery: 291-342 (82.4 - 96.8%) -- guaranteed 2HKO after Leftovers recovery
Dugtrio Earthquake vs. Raichu: 267-314 (82.6 - 97.2%) -- guaranteed 2HKO after Leftovers recovery
Raichu Surf vs. Dugtrio: 161-190 (58.9 - 69.5%) -- guaranteed 2HKO after Leftovers recovery
Mr. Mime Psychic vs. Raichu: 113-133 (34.9 - 41.1%) -- 68.8% chance to 3HKO after Leftovers recovery
Raichu Thunder vs. Mr. Mime: 107-126 (37.8 - 44.5%) -- guaranteed 3HKO after Leftovers recovery
Light Ball Pikachu Surf vs. Raichu: 106-125 (32.8 - 38.6%) -- 4.4% chance to 3HKO after Leftovers recovery
Raichu Surf vs. Pikachu: 108-127 (39.5 - 46.5%) -- guaranteed 3HKO
Raichu Surf vs. Raichu: 74-88 (22.9 - 27.2%) -- possible 5HKO after Leftovers recovery
Poliwrath
Poliwrath has access to the combination of Lovely Kiss + Belly Drum while also having solid defenses. Its Speed is a bit lacking, but those traits should in theory still be strong in any tier. In UU, Slowbro is a big problem for Poliwrath since it lives anything Poliwrath can throw at it, even at +6, and KOs in return with Psychic. There are also a lot of Pokemon that outspeed and threaten to hit it hard, such as Electabuzz, Dodrio, Haunter, Kadabra, Mr. Mime, Pikachu, Nidoqueen, etc. Thanks to its defenses, a couple of those Pokemon fail to KO with their most powerful attacks even after Belly Drum. However, considering the number of Sleep Talk users, the possibility of Haze users such as Qwilfish and Crobat, and other issues, Poliwrath has failed to gain a foothold in the tier. It also does not help that Quagsire makes a better Speed boost recipient despite Poliwrath's access to Lovely Kiss.
If it were available to use in NU, I think it would be unlikely to pose a significant threat without receiving a Speed boost, but the current metagame from what I have seen does not make a significant effort to stop Speed passing. It is of note that Poliwhirl is also allowed in GSC NU, and barely sees any use despite being faster and having similar LK+BDrum options available to it. It would probably not make an effective Curse user, since Hitmonchan/Hitmontop have better stats, but it would have the niche of being resistant to Water and Ice attacks from Octillery and Dewgong, in exchange for the Electric and Grass weaknesses. So I am uncertain about whether it would be too strong, leaning towards not.
Mr. Mime Psychic vs. Poliwrath: 211-248 (55 - 64.7%) -- guaranteed 2HKO after Leftovers recovery
Poliwrath Hidden Power Ghost vs. Mr. Mime: 120-142 (42.4 - 50.1%) -- guaranteed 3HKO after Leftovers recovery
Light Ball Pikachu Thunderbolt vs. Poliwrath: 296-348 (77.2 - 90.8%) -- guaranteed 2HKO after Leftovers recovery
Light Ball Pikachu Thunder vs. Poliwrath: 372-438 (97.1 - 114.3%) -- 84.6% chance to OHKO after Leftovers recovery
Dugtrio Earthquake vs. Poliwrath: 97-114 (25.3 - 29.7%) -- 0% chance to 4HKO after Leftovers recovery
Golduck
Golduck has fairly well-rounded stats and a somewhat interesting movepool, learning Cross Chop and Hypnosis. Its speed enables it to outspeed and threaten Nidoqueen in GSC UU, but it is not likely to be able to threaten any of the Pokemon that would switch into it, which often are Restalkers. Similarly, there are many strong Sleep Talk users in GSC NU, meaning it will likely struggle to do anything better than running its own Restalk set in GSC NU. Also, it's likely to be less effective at Restalking than Dewgong or Octillery due to neither its SpA stat nor its defenses standing out as being particularly high in comparison. Its higher speed is also not likely to help it too much, since it is still slower than Pokemon like Mr. Mime, Pikachu, Haunter, Pidgeot, Fearow, etc. It does have the (somewhat) interesting option of using Counter, but this would be far from a reliable option. I have no doubt that Golduck would fit into NU perfectly fine.
Ninetales
Lastly, we come to Ninetales. In GSC UU, it is almost completely useless due to the ubiquity of Slowbro/Slowking. There is almost no reason to consider using it. In GSC NU, the Pokemon that immediately comes to mind to compare it to is Rapidash. Rapidash is not such a great Pokemon in GSC NU, since its defenses are on the low side and it struggles to break water types, even when it activates Sunny Day, because it doesn't learn SolarBeam. Ninetales does not learn SolarBeam either, but it has higher defenses, and trades Rapidash's mostly useless Attack stat for higher SpD, HP, and Def stats. In terms of movepool, both have Hypnosis and the same offensive options, but Ninetales learns a few extra support moves in Roar (which also synergises well with potentially using Toxic), Confuse Ray, and Disable. Roar is definitely interesting, and more viable Roar users would certainly be welcome in the tier. Its high SpA and SpD allow it to potentially go toe-to-toe with Mr. Mime (at a possible cost of having to use Restalk to compete with Restalk Mr. Mime), but it would still fear tier staples like Dugtrio and Octillery. I think there is no reason that Ninetales should not be allowed in GSC NU.
I am hoping the RoA community can assist in determining which Pokemon should stay in their current tiers and which should swap their status. Note that I am not looking to change the GSC UU metagame at all.
My personal opinion about how this should be handled is, the Pokemon currently in the tier should be kept, and the Pokemon that would not be overwhelming for the tier should be dropped into NU. I have some attachment to the current metagame, having built probably more than 20 teams in it and won the GSC NU tournament, and I think that Mr. Mime, Pikachu etc are representative of the tier. However, I'm pretty sure there are others with different opinions about how it should be handled. Another possibility I thought of is, hold a poll for each Pokemon listed above where any Smogon user can vote, then host a bo3 single elimination GSC NU tournament with the changes as a result of that poll enacted, then finally allow all participants who played their games in the tournament to vote on the final tiering.
If anyone has any suggestions, please post them, as well as obviously any opinions on the Pokemon themselves and how strong they are/would be in NU.
Now that GSC UU has gained exposure from UUPL, a more official viability ranking thread has been created, and the creation of GSC PU based on the (antiquated) Viability Rankings in the GSC NU forum as well as tiering debates about what should be included in PU have now also brought attention to the fact that GSC NU was created fairly arbitrarily. At the point that GSC NU was created, I would say that the GSC UU metagame was much less developed than it is now, and I think there are some Pokemon that should have made the cutoff for NU that remained UU. Ellicrum has helpfully provided a list of Pokemon that are listed as UU but not included on the viability ranking list, despite numerous NU Pokemon being included (a couple even being in A- and B).
Disjunction who seems to lead GSC NU in the NU forums has not logged in for a while, and our friendly RoA moderator Jellicent has no objections to discussion of potential tiering changes, so below are the candidates and how I perceive them to fare in the relevant metagames. I will be converting my personal NU viability rankings into the S/A/B/C/D system and comparing those against the UU viability rankings, rather than using the rankings in the NU forum.
Pokemon ranked B or above in both tiers
Pikachu
UU: B, NU: A
Pikachu is obviously very powerful, hitting about as hard as Zapdos. In UU, which is a relatively slow tier with lots of bulky hard-hitters, several of which are Water-types, Pikachu's strengths can shine, which enables it to achieve as high as B rank in GSC UU. In NU, where a lot of Pokemon are faster than Pikachu and two of the best Pokemon in the tier outmatch it, it comes in at A. The NU metagame has evolved around Pikachu, which has led to the rise of Dugtrio and other Pokemon that are faster, which has in turn caused Pikachu to sometimes turn into more of a liability than a useful Pokemon - one would often rather have a Pokemon they can actually switch into attacks, and stall teams tend to have it well covered. That said, its effect on the metagame should not be understated, and teams that are underprepared for it can easily be put into very dicey situations against it.
Mr. Mime
UU: A-, NU: A+
Mr. Mime is a Pokemon that brings a lot of utility to the table, with a multitude of possible sets available to it. It has a solid 100 base SpA, and the Pokemon that can wall its attacks in UU can do little about it spreading status or Baton Passing boosts to another Pokemon. In NU, Mr. Mime is clearly one of the strongest Pokemon in the tier, with very few viable Pokemon able to reliably handle it outside of itself. Psychic resists other than Mr. Mime are few and far between, and those that do resist it are mostly demolished by Thunderbolt. However, it does have a very low Defense stat, which can make it difficult to find an opportunity to come in without taking a lot of damage, except against itself. Additionally, it runs the risk of facing Thunder Wave or Shadow Ball Mr. Mime, both of which will make it even more susceptible to other threats. That said, a Pokemon whose best counter is itself does not tend to make for a healthy addition to a tier, so it was arguably a mistake to include Mr. Mime in the first place.
Haunter
UU: A-, NU: A-
I am not sure Haunter deserves such a high rank in the UU viability rankings. I'm presuming it is because of how powerful Granbull is as well as its access to Hypnosis and Explosion and coverage moves that are super effective against the tier's strongest Pokemon. Looking at the UUPL cumulative stats, it had a 37.5% win rate and was used 8 times. In GSC NU, it is quite useful because of its Shadow Ball hitting Mr. Mime hard while also being faster, and the normal and poison immunities are handy against Normal-types and Shuckle. However, Dugtrio switches into it relatively freely if it doesn't get caught by Hypnosis, and it is quite fragile. It can also have 4MS with Explosion/SBall/Tbolt/Psychic/Hypnosis, all of which are highly useful to pose a threat to relevant top tier Pokemon. The NU tier does not have any significant issues handling Haunter.
Unranked UU Pokemon that are currently banned from NU
Omastar
This Pokemon has very high SpA and is probably viable in UU. In theory, it should be able to come into a Granbull and dish out damage to anything that comes in, especially with Spikes up. However, unfortunately its typing and HP/SpD stats don't allow it to switch into much other than Normal-types.
Omastar Surf vs. Granbull: 156-184 (40.7 - 48%) -- guaranteed 3HKO after Leftovers recovery
Omastar Surf vs. Nidoqueen: 251-296 (65.5 - 77.2%) -- guaranteed 2HKO after Leftovers recovery
Omastar Hidden Power Electric vs. Slowbro: 131-154 (33.3 - 39.1%) -- guaranteed 3HKO after Spikes and Leftovers recovery
Omastar Surf vs. Ampharos: 122-144 (31.8 - 37.5%) -- 93.4% chance to 3HKO after Spikes and Leftovers recovery
In NU, I am pretty sure it would smack pretty much everything around while also resisting the STAB attacks of the many powerful Normal types (unlike Octillery/Dewgong). There is no way this thing fits in the current tier.
Omastar Hidden Power Grass vs. Octillery: 134-158 (37.9 - 44.7%) -- guaranteed 3HKO after Spikes and Leftovers recovery
Omastar Surf vs. Mr. Mime: 100-118 (35.3 - 41.6%) -- guaranteed 3HKO after Spikes and Leftovers recovery
Omastar Surf vs. Lickitung: 136-160 (35.5 - 41.7%) -- guaranteed 3HKO after Spikes and Leftovers recovery
Omastar Hidden Power Grass vs. Dewgong: 115-136 (30 - 35.5%) -- 31.4% chance to 3HKO after Spikes and Leftovers recovery
Hitmonlee
Hitmonlee is basically like Hitmonchan, which is a solid and balanced NU Pokemon, but with a much better stat distribution (Hitmonchan has 26 higher base Def, from which 15 went into Attack and the other 11 went into Speed for Hitmonlee). Importantly, Hitmonlee is no less bulky on the Special side. Hitmonlee also has access to Meditate which allows it to boost its own attack without sacrificing its Speed. Fighting is not a particular good type in UU, with a lot of the strongest Pokemon resisting it, and Hitmonlee does not learn Earthquake for Nidoqueen, nor does its Reversal set particularly scare Slowbro. In NU, even with its higher speed, it would still be slower than many common Pokemon in the metagame. However, while Mr. Mime is not too scared of switching into Hitmonchan once (even if it ends up tanking HP Ghost), Hitmonlee's attacks are more punishing:
Hitmonchan Hidden Power Ghost vs. Mr. Mime: 137-162 (48.4 - 57.2%) -- 47.7% chance to 2HKO after Leftovers recovery
Hitmonchan High Jump Kick vs. Octillery: 114-135 (32.2 - 38.2%) -- 0.9% chance to 3HKO after Leftovers recovery
Hitmonlee Hidden Power Ghost vs. Mr. Mime: 149-176 (52.6 - 62.1%) -- 99.8% chance to 2HKO after Leftovers recovery
Hitmonlee High Jump Kick vs. Octillery: 125-147 (35.4 - 41.6%) -- 80.8% chance to 3HKO after Leftovers recovery
It could be argued that this is a good thing, since it will encourage more people to use Xatu instead of Mr. Mime. I think it is hard to tell if Hitmonlee would be too strong for GSC NU at this point.
Dugtrio Earthquake vs. Hitmonlee: 136-160 (44.8 - 52.8%) -- 86.5% chance to 2HKO after Spikes and Leftovers recovery
Raichu
Raichu is fast and has a pretty solid SpA stat, plus access to Surf. This should in theory allow it to do decent damage to Nidoqueen while dominating Slowking, which is a highly desirable trait in GSC UU. However, its defenses are lacking and it only manages 41.9 - 49.3% against Nidoqueen with Surf, while Nidoqueen almost OHKOs in return with Earthquake. Teams with Ampharos or Hypno essentially wall it permanently, and there are not many Pokemon it can switch into safely. It is not hard to imagine why it does not see a lot of use and has not been listed on the viability rankings.
Raichu obviously does significantly less damage than Pikachu does, so should not be as threatening in GSC NU. However, it is also significantly harder to take down than Pikachu, living an Earthquake from Dugtrio while 2HKOing it with Surf, and being 3HKOed instead of 2HKOed by Mr. Mime, albeit having to rely on Thunder for a chance at 3HKOing in return. It would have plenty of defensive counter options, and would not be able to touch Grass-types if it chooses to use a Restalk set with Surf. It would also potentially make a good Pikachu counter. I would say it would be quite strong in the tier, but it is not clear if it would be overpowered.
Octillery Surf vs. Raichu: 125-147 (38.6 - 45.5%) -- guaranteed 3HKO after Leftovers recovery
Raichu Thunder vs. Octillery: 291-342 (82.4 - 96.8%) -- guaranteed 2HKO after Leftovers recovery
Dugtrio Earthquake vs. Raichu: 267-314 (82.6 - 97.2%) -- guaranteed 2HKO after Leftovers recovery
Raichu Surf vs. Dugtrio: 161-190 (58.9 - 69.5%) -- guaranteed 2HKO after Leftovers recovery
Mr. Mime Psychic vs. Raichu: 113-133 (34.9 - 41.1%) -- 68.8% chance to 3HKO after Leftovers recovery
Raichu Thunder vs. Mr. Mime: 107-126 (37.8 - 44.5%) -- guaranteed 3HKO after Leftovers recovery
Light Ball Pikachu Surf vs. Raichu: 106-125 (32.8 - 38.6%) -- 4.4% chance to 3HKO after Leftovers recovery
Raichu Surf vs. Pikachu: 108-127 (39.5 - 46.5%) -- guaranteed 3HKO
Raichu Surf vs. Raichu: 74-88 (22.9 - 27.2%) -- possible 5HKO after Leftovers recovery
Poliwrath
Poliwrath has access to the combination of Lovely Kiss + Belly Drum while also having solid defenses. Its Speed is a bit lacking, but those traits should in theory still be strong in any tier. In UU, Slowbro is a big problem for Poliwrath since it lives anything Poliwrath can throw at it, even at +6, and KOs in return with Psychic. There are also a lot of Pokemon that outspeed and threaten to hit it hard, such as Electabuzz, Dodrio, Haunter, Kadabra, Mr. Mime, Pikachu, Nidoqueen, etc. Thanks to its defenses, a couple of those Pokemon fail to KO with their most powerful attacks even after Belly Drum. However, considering the number of Sleep Talk users, the possibility of Haze users such as Qwilfish and Crobat, and other issues, Poliwrath has failed to gain a foothold in the tier. It also does not help that Quagsire makes a better Speed boost recipient despite Poliwrath's access to Lovely Kiss.
If it were available to use in NU, I think it would be unlikely to pose a significant threat without receiving a Speed boost, but the current metagame from what I have seen does not make a significant effort to stop Speed passing. It is of note that Poliwhirl is also allowed in GSC NU, and barely sees any use despite being faster and having similar LK+BDrum options available to it. It would probably not make an effective Curse user, since Hitmonchan/Hitmontop have better stats, but it would have the niche of being resistant to Water and Ice attacks from Octillery and Dewgong, in exchange for the Electric and Grass weaknesses. So I am uncertain about whether it would be too strong, leaning towards not.
Mr. Mime Psychic vs. Poliwrath: 211-248 (55 - 64.7%) -- guaranteed 2HKO after Leftovers recovery
Poliwrath Hidden Power Ghost vs. Mr. Mime: 120-142 (42.4 - 50.1%) -- guaranteed 3HKO after Leftovers recovery
Light Ball Pikachu Thunderbolt vs. Poliwrath: 296-348 (77.2 - 90.8%) -- guaranteed 2HKO after Leftovers recovery
Light Ball Pikachu Thunder vs. Poliwrath: 372-438 (97.1 - 114.3%) -- 84.6% chance to OHKO after Leftovers recovery
Dugtrio Earthquake vs. Poliwrath: 97-114 (25.3 - 29.7%) -- 0% chance to 4HKO after Leftovers recovery
Golduck
Golduck has fairly well-rounded stats and a somewhat interesting movepool, learning Cross Chop and Hypnosis. Its speed enables it to outspeed and threaten Nidoqueen in GSC UU, but it is not likely to be able to threaten any of the Pokemon that would switch into it, which often are Restalkers. Similarly, there are many strong Sleep Talk users in GSC NU, meaning it will likely struggle to do anything better than running its own Restalk set in GSC NU. Also, it's likely to be less effective at Restalking than Dewgong or Octillery due to neither its SpA stat nor its defenses standing out as being particularly high in comparison. Its higher speed is also not likely to help it too much, since it is still slower than Pokemon like Mr. Mime, Pikachu, Haunter, Pidgeot, Fearow, etc. It does have the (somewhat) interesting option of using Counter, but this would be far from a reliable option. I have no doubt that Golduck would fit into NU perfectly fine.
Ninetales
Lastly, we come to Ninetales. In GSC UU, it is almost completely useless due to the ubiquity of Slowbro/Slowking. There is almost no reason to consider using it. In GSC NU, the Pokemon that immediately comes to mind to compare it to is Rapidash. Rapidash is not such a great Pokemon in GSC NU, since its defenses are on the low side and it struggles to break water types, even when it activates Sunny Day, because it doesn't learn SolarBeam. Ninetales does not learn SolarBeam either, but it has higher defenses, and trades Rapidash's mostly useless Attack stat for higher SpD, HP, and Def stats. In terms of movepool, both have Hypnosis and the same offensive options, but Ninetales learns a few extra support moves in Roar (which also synergises well with potentially using Toxic), Confuse Ray, and Disable. Roar is definitely interesting, and more viable Roar users would certainly be welcome in the tier. Its high SpA and SpD allow it to potentially go toe-to-toe with Mr. Mime (at a possible cost of having to use Restalk to compete with Restalk Mr. Mime), but it would still fear tier staples like Dugtrio and Octillery. I think there is no reason that Ninetales should not be allowed in GSC NU.
I am hoping the RoA community can assist in determining which Pokemon should stay in their current tiers and which should swap their status. Note that I am not looking to change the GSC UU metagame at all.
My personal opinion about how this should be handled is, the Pokemon currently in the tier should be kept, and the Pokemon that would not be overwhelming for the tier should be dropped into NU. I have some attachment to the current metagame, having built probably more than 20 teams in it and won the GSC NU tournament, and I think that Mr. Mime, Pikachu etc are representative of the tier. However, I'm pretty sure there are others with different opinions about how it should be handled. Another possibility I thought of is, hold a poll for each Pokemon listed above where any Smogon user can vote, then host a bo3 single elimination GSC NU tournament with the changes as a result of that poll enacted, then finally allow all participants who played their games in the tournament to vote on the final tiering.
If anyone has any suggestions, please post them, as well as obviously any opinions on the Pokemon themselves and how strong they are/would be in NU.