This should be my last sort of big round-up/commentary post.
Corrosion: Corrosion is far too limited. While it does allow us to beat Toxapex and Mollux easily, much like Salazzle, Corrosion on a Fire type is just silly. Half the time you will be seeking burns (or DBreath paralysis), and while my opinion on this this would be entirely different if Heatran were currently part of the metagame, it isn't and therefore it isn't proper to bring it up. We don't even get the perfect accuracy on Toxic because 27 isn't Poison type. Not the right ability for this CAP.
Grassy Surge: One critical flaw of Grassy Surge is that it also provides immense support for your opponent. 5 turns of healing for grounded opponents really messes with your calculations, especially since huge portions of our pressure and C+C list are grounded. While 27 itself has no issues taking a boosted Grass attack, that might not be true for the rest of your team. You have to avoid teammates that would be negatively impacted by Grassy Surge, which would include any number of bulky waters you might want to keep in the back, and any offensive partners that can't afford grounded opponents getting double leftovers recovery. Grassy Surge limits the number of offensive cores you could use with 27.
Natural Cure: CAP is a metagame with a great deal better options on status absorption, given how often it was brought up in many past discussions. Krilowatt, Colossoil, Naviathan, Pajantom, and Snaelstrom all provide this, Kefluffle has Natural Cure itself, Mollux absorbs everything that isn't paralysis, and Fidgit absorbs most practical instances of Poison and Paralysis without fearing burn-inducing Fire attacks [Scald tho...]. I don't think Status Absorption is a useful consideration for 27. [Historical Note: In BW LumHarvest Malaconda was also a Status Absorption Pokemon.]
Levitate: After some consideration, it is really difficult to discount the usefulness of Levitate. Immunity to Spikes and Toxic Spikes without needing Heavy-Duty Boots are an immense boon, and give CAP the same kind of general switch-in ability as something like Mandibuzz. While I am usually critical of such immunity abilities, in this instance (and unlike Equilibra where I preferred Bulletproof primarily), we have a typing that has a pretty specific resistance profile and a lot of neutralities.
One thing that does concern me about Levitate is it has an incredible effect on our C+C list, nullifying all of the Ground-types there. Hippowdown is forced to Whirlwind and rely on Rocks damage (and HDB is still good for ignoring that). Opponents relying on Ground coverage are neutralized. That said, a Rock weakness is still very exploitable, and 27 doesn't actually resist Water so those matchups are less effected.
Still, I think it is very powerful, but it expands options rather than heavily biases 27 to one way of play or another.
Multiscale: I think Support Dragonite is a really excellent parallel now that Heavy-Duty Boots exists. While Leftovers is generally preferable given 27's larger hazard vulnerability, Multiscale is excellent at providing that initial buffer to get a support move off. Fire STAB is more aggressive than Flying and the resistance/neutrality profile is much better with no 4x weaknesses, and not having an entire type resistant to both (Steel in Dragonite's case).
Neutralizing Gas: I know I made the initial post on this, but
Orig Stall Guy expanded on it. Neutralizing Gas is basically Mold Breaker on steroids. If we look at the viability rankings, we can see it has a massive impact:
SS Viability Rankings said:
S Rank:
S Rank
Clefable -
Takes Hazards on Switchin, vulnerable to Toxic weardown, Unaware set mostly unaffected.
Corviknight - Scared away, not losing PP to Pressure just a bonus.
A Rank:
A+ Rank
Aegislash - Not affected, Stance Change can't be neutralized.
Dragapult - Only marginal benefits. Fire Lash will lower Def, or Infiltrator won't bypass Sub.
Equilibra -
Takes Spikes damage.
Kyurem - Marginal benefit.
Terrakion - Irrelevant other than not giving it an Attack Boost if we throw Knock Off out.
Toxapex - Needs to use Recover to heal, can't switch camp for Regenerator recovery.
This helps other breakers get through it even though it still walls 27.
A Rank
Hydreigon -
Takes Spikes Damage.
Mandibuzz - Takes Sandstorm damage I guess, and you can hit it with Powder-based Statuses.
Mollux - Irrelevant, Mollux doesn't even have listed Rain partners.
Rotom-Heat -
Takes Spikes Damage.
Seismitoad - Irrelevant before Movepool considerations.
Syclant -
Takes HUGE Rocks Damage.
Tomohawk -
Disables Prankster or Intimidate, greatly limiting walling potential.
Zeraora - Irrelevant.
A- Rank
Arghonaut - Irellevant.
Colossoil -
Crippled by Burn Orb instead of boosted, though EQ will still be nasty.
Conkeldurr -
Crippled by Burn Orb instead of boosted.
Excadrill -
Depends on Stats, but nullifies Sand Rush.
Ferrothorn -
Nullifies Iron Barbs.
Jumbao - Potential drawback in nullifying / delaying Drought. Trace activates on follow-up switch.
B Rank:
B+ Rank
Aurumoth -
Nullifies Weak Armor and No Guard.
Bisharp -
Nullifies Defiant boosts.
Hippowdon - Suspends Sandstorm if not already out, which is a potential drawback due to the delay.
Jirachi -
50% Less Hax.
Kommo-o - Likely Irrelevant.
Mamoswine -
Nullifies Thick Fat so Fire moves hit at SE Strength.
Necturna -Irrelevant. Runs Away anyway.
Stratagem -
Takes Spikes Damage.
B Rank
Ditto -
Suppresses Imposter, but doesn't nullify an existing transformation. Imposter will fire after 27 leaves so switch appropriately.
Dracovish -
Cuts Power dramatically, especially if 27 is faster. Band Rend will still hit ridiculously hard on switchin though.
Gastrodon - Irrelevant before movepool considerations.
Gengar - Irrelevant
Keldeo - Irrelevant
Kerfluffle -
Statusing Kerfluffle will stick if CAP is active when it switches.
Naviathan -
Crippled by Burn Orb instead of boosted.
Pajantom - Irrelevant, Comatose ignores Neutralizing Gas.
Reuniclus -
Takes Hazards on Switchin, vulnerable to Toxic weardown.
Tyranitar - Suspends Sandstorm if not already out, which is a potential drawback due to the delay.
It should be plain to see, especially if 27 has a partner with Spikes that Neutralizing Gas is a phenomenal offensive support ability that compromises the effectiveness of a large number of S-B Rank Pokemon, punishing them if they come in or are in while 27 is on the field (
this matters in double switch prediction scenarios especially).
While it does have some interactions with fat Pokemon like Toxapex, Pex still has the option to hard Recover, and can still remove our item with Knock Off and cripple us with Toxic. Not having Regenerator activate for it though makes it much easier for breakers in an offensive core to finish it off, even though 27 can't finish it by itself.
Bottom Line: Neutralizing Gas is a very relevant offensive support ability that should not be overlooked given the current makeup of the metagame.
Serene Grace: One more once-over on Serene Grace. Serene Grace answers question 4):
4) What is more important for our CAP to fulfill its role as an offensive support: an ability which accentuates its defensive utility and ability to support its team, or its synergy with certain items?
Serene Grace answers that definitively with accentuating defensive utility. While Serene Grace inherently makes movepool assumptions, those assumptions can be generalized as 60-100% chances of powerful negative status while using damaging attacks, a significant upgrade to nearly all Fire-type attacks, and in general striking a balance in favor of weaker attacks with higher effect chances.