Yay! Just want to say right away that it's about time! As far as I know, most of these clauses are just collateral damage from OU bans (Moody being the obvious exception). So pent-up essay go! [rant]
The Ubers metagame is characterized by its lack of concern for centralization, but there is a rather lengthy list of serious threats to consider when teambuilding, and there are likely hundreds of viable teams. How might releasing these clauses affect the metagame? Let's see....
OHKO moves are terrifying for everyone involved. Outright disposing of an opposing Pokemon is a really big deal. But there's always that 70% chance that the user will miss and grant the opponent a free turn, which can be equally as devastating. OHKO moves inject a big element of luck into many matchups. Then again, not that many Pokemon can afford to run an OHKO move rather than some other option. Kyogre, Gliscor, Excadrill, Hippowdon, Groudon, and arguably Dugtrio, Lapras, and Articuno are pretty much the only Pokemon that might be a problem. Stallish Kyogre already exists, and Sheer Cold is a serious option for it. Guillotine Gliscor is interesting, but it still ultimately loses to Pressure stallers like Giratina and fast Ho-Oh. Excadrill and Groudon are usually better off just running a coverage or support move. Hippowdon too somewhat, but at least it has reliable recovery so it could work. Lapras and Articuno are just gimmicky, and they both are annihilated by Thunder and other common coverage moves. Dugtrio is if you're incredibly desperate, but if you are bold enough to use Duggy in Ubers then you might as well give it Fissure. Hardly anyone will lock themselves into Electric attacks when your opponent sees your team anyways. Since it seems unlikely that Sheer Cold Kyogre will dominate the metagame, I could easily see OHKO Clause lifted and there still being a perfectly enjoyable metagame.
Pointless Brightpowder ban was pointless. But seriously, how might Double Team and Minimize affect things? First thing to note is that in Ubers, Thunder is on basically every team, and Aura Sphere is not uncommon. As other perfect-accuracy moves go, most of them have little use. Abomasnow and other Hail abusers such as Kyurem-W have Blizzard, which is cool, but Abomasnow has to really watch its step so that it doesn't die. Shadow Force has gone out of style and doesn't look like it's going back. I think I faced someone with a Faint Attack Weavile before, but lol. So the point is, the list of perfect-accuracy moves is essentially Thunder in rain, Aura Sphere, and Abomasnow's Blizzard. These are all special attacks, so that implies that Calm Mind users may have a use for it. As a veteran of Challenge Cup, I can say that evasion-boosting moves suck without a recovery move, so that only would leave one free moveslot. For most Pokemon this is a serious flaw, but some Pokemon may make it work, like Giratina or Latias. Then, there's the matter of Baton Pass chains. DT/Minimize are perfectly valid, and the fact that Roar and Whirlwind can miss is just dandy. The big hurdle is that it takes some serious time to rack up enough Evasion boosts for it to be worthwhile, but all it takes is a lucky miss to start going down the drain . If you play your cards right, then there is a very good chance that such a Pokemon can make such a stand.
That is, unless the opponent has a certain oft-overlooked move: Perish Song
. If you start boosting up, and your opponent has Perish song, then no number of Double Teams can save you from death. If you rely on evasion boosts and you opponent has an Arceus or Celebi with Perish song, you lose. Overcentralization is of no concern to Ubers, so not preparing for DT is ultimately the teambuilder's fault. Toxic can also help, as lost as the booster does not have Rest. Not being willing to give up a teamslot for a subpar Arceus or Celebi (or Meloetta or Mismagius) is like refusing to put a spinblocker on a team, except much worse. We'll just have to see, but the liability of having a Perish Song-er is essentially a question of whether is is better to have a slightly inferior team that beats gimmicks, or have a good team that allows some matches to turn into frustrating luckfests. It is probably for the best that Evasion Clause is here, but if Perish song gets popular, then Double Team and Minimize suddenly suck. The metagame will decide.
Ah, this takes me back when I crushed the unfortunate souls of many a new Ubers player with a Moody Octillery. Then Smeargle got released, and Moody was confirmed to be the worst thing ever in the history of competitive play, and was purposefully banned from Ubers through a battle clause. Perish Song, Toxic Spikes, and a prayer seem to be the only things that can knock out a Moody Bibarel or Octillery (Haze still is not that useful, because these Pokemon can fight back). As for Moody Smeargle, not even almighty God can help you when it sets up a sub. It's Perish Song or death. The best answer to Moody is impeccably good prediction skills, and even that usually fails. Since then, the metagame seems to have gotten less stallish, so I can see why this clause is on the table. I'm all for testing Moody again, I just don't think anything significant has changed.
Ye olde Sleep Clause seems to be a bit different from the first few clauses. The only things in Ubers that would currently dare use a sleep-inducing move are Darkrai and Smeargle. Breloom could see a serious short-term rise. Parasect is interesting as well, but it is super slow. I almost forgot Jumpluff exists, but it can be equally as terrifying in the absence on Sleep Clause (especially if Evasion Clause is lifted). Brace yourself for a big metagame shift if this clause gets revoked. Everything except Wobbuffet can use Sleep Talk, so expect random Pokemon to suddenly carry it, like Ho-Oh. Rest-Talking may make a comeback, then things will carry Taunt. Alternatively, players will start slapping Lum Berry on everything...all this is metagame stuff. The big question is whether such a metagame would be at all desirable. All this based on a move with 80% accuracy. There's the chance of missing, the number of sleep turns, and the move that Sleep Talk picks. All of this leads to luck being a bigger factor in games. The big question is whether Ubers players are willing to accept that they have to run Lum Berry or Sleep Talk over "better" options. Sleep Clause is really starting to push it for removing clauses. We will be left with a StreetPKMN-like metagame, which is different to be sure, but imo not end-of-the-world-as-we-know-it terrible.
There is the perception that Species Clause is the sole reason that Ubers is a good metagame to play in. Everything has its own list of checks and counters, some more so than others. It is the "others" that is the concern here. When a whole team is involved, there is a tendency to look and say, "Oh, my opponent has that Pokemon that my team can't handle well! Looks like I have to do A and B and hope things go smoothly." When Species Clause is taken away and you look down the barrel of 3 or 4 Arceus smiling at you in team, then you will see fear itself. But if you are smart, then you too will put the best Pokemon for the job on your team. It all cancels out. What's left though is the kind of centralization that makes players of lesser tiers weep. Since theoretically Ubers is not based on the idea of avoiding centralization, this new metagame would not be undesirable in that regard. What will happen is a brand new set of strategies centered around arguably the most terrifying Pokemon in existence: Arceus.
The funny thing about team preview is that it shows you all the Pokemon on the opponent's team right down to the forme except for you-know-who. And each type of Arceus plays differently! Arceus can assume any type it wishes complete with a prepackaged base 100 STAB move, a deep movepool, and base 120 stats all around. Each Arceus forme plays like a different Pokemon, and team preview utterly fails. Even though Arceus is really good, it would be foolish to use an all Arceus team. Why? Because there are many roles that teams enjoy that cannot be filled by Arceus. I could see a decent player using up to 3 Arceus formes. Any more than that means kicking off a more useful teammate. Arceus does not have the tankiness of Giratina, the immediate field support of Kyogre, and so on. Extremekiller is a big metagame force. It can be checked and even countered, but it takes its toll on most teams. With the right set and support, a +2 Arceus can take down literally anything before being KOed. Having multiple Extremekillers to play with can get ugly really fast. So everyone is forced to constantly put pressure on Extremekiller to keep from getting swept. In truth, this could be said about many Ubers Pokemon.
Enough about Arceus, back to Species Clause. So it centralizes the metagame, which Ubers players aren't supposed to care about. What's the big fuss about then? No matter how broken a team is, you can always answer it with the exact same team. That's what I think is the real thing to be cautious of. If it gets to the point where the metagame is essentially one team, then it turns the competitive game of Pokemon and turns each game into a big coinflip. If people wanted that, then they would play a game like War
rather than Pokemon. That is why too much centralization is a bad thing, even in Ubers. But I have a hard time believing that that would be the eventual outcome if Species Clause were removed. It might shake up the metagame by introducing exciting new tactics and strategies, so taking advantage of concealing team members and overall skill would be even more rewarded. Alternatively, it might destroy the diversity of Ubers and thus make battling less fun and more of a chore. In my opinion, it is more likely that eliminating Species Clause would bring about more harm than good. But as always I am excited to test this stuff out for real. The future is awesome! [/rant]