One thing to note is, depending on how the suspect voting goes, Sceptile-Mega’s usage will plummet if it loses Contrary.
So unless a new set is discovered, as I doubt it’s own current list of sets will keep it in the position it is currently in, it needs to drop; Contrary was it’s main saving grace.
Although, I could still see Dazzling sets serving a purpose for Spore, and anti-Kyogre-Primal Coverage (plus it checks -ate Diancie-Mega with Seed Flare). Although one could argue Tough Claws Beedrill with Bolt Strike can handle Kyogre-Primal, and is also able to pull off a Dazzling Set with Choice Band and KO Diancie with Sunsteel.
MMY will lose some usage as well as Contrary was its most potent set. It will still be highly ranked, but losing the most powerful of offensive sets is a hit to anything that used it, even if it didn’t depend on it like Sceptile-Mega did.
Further, I could see niche Pokémon like Necrozma-Ultra losing some usage as Contrary made it relevant for its 2-in-1 Draco Meteor + Psycho Boost / Photon Geyser STAB coverage.
My predictions regarding if Contrary gets banned:
I think the bigger change, however, is how much Unaware and Prankster Haze will rise as they now have an easier time handling all sweepers. For example, now Prankster Sap Strength Giratina and any Unaware Sap Strength user can avoid worrying about boosting Contrary MMX and it’s Photon Geyser.
Moldy Moves will still plague Unaware users, like Sunsteel Strike vs Unaware Audino-Mega, but at least they won’t be a guaranteed threat when we see how common a defensive check Prankster and Unaware will be: I.e. Registeel takes nothing from Sunsteel, and Photon Geyser. From here, I could see more Flash Fire and Magic Bounce variants rising, as well as more Steels in general like Flash Fire Aegislash and Dusk-Mane, thanks to its ability to check MMX, which will be less likely to carry Moongeist Beam.
The other thing that will rise is the use of other types of sweeping such as Sheer Force MMY, which undermines the commonality of Set-up checks. Unburden and (Simple) Smash sets will drop, however, as counterplay for setups will be more omnipresent, and instead Choice users like Specs Aerilate Ray, etc. will go up in usage, thus Scarf Imposter will rise again as there will be less Imposterproof sweeping (like Unburden) to deter it.
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Side note on Imposter mechanics—
Yeah just tested extensively with
ScarfWynaut and if you imposter a groudon with a red orb imposter nothing much happens regardless of species. If you Imposter a Pokémon while you are holding the imposters own mega stone after transforming it can mega into the Imposters mega form getting it's stats, ability and typing but keeping the moveset you copied.
Most interestingly if you have an imposter Rayquaza that knows dragon ascent before impostering, then after transforming it can mega into a Mega Rayquaza, however if the imposter Rayquaza doesn't know dragon ascent but the thing it copied did it still can't mega.
Further testing shows if the Imposter holds a z-crystal as long as the appropriate move is in the copied moveset it can use it, including signature moves such as ss7ss.
For other form changes: an imposter in the form of meloetta never changes form, it stays as what it copied; an imposter of Darmanitan also never changes form even if you get a zen mode darmanitan and give it transform; an impostered aegislash also doesn't change form.
just to add, a transformed pokemon can use the exclusive z move of its transformed state, but not one of its original form. I think this is to say exclusive z's check the user's current form like hyperspace fury but not base species.
I found this old set of data and wanted to consider if you consider Imposter on Pokémon that gains Mold Breaker as it Megas.
For example, let’s consider Gyarados Imposters Shell Smash Dusk-Mane with Flash Fire. It can Mega Evolve to remove its Steel and Psychic Typing to gain a resistance to Power Trip, Sunsteel Strike, and Photon Geyser.
Through Mold Breaker, it can use Power Trip not only break Necrozma-Dusk-Mane, but also Unaware and Fur Coat users. It also doesn’t need Flash Fire due to its typing.
The trick is to give Gyarados moves that will be useful after it Mega Evolves, (such as Stealth Rocks) for when it switches out and back in again.
Now, since you copy the moveset of whatever you imposter even after you Mega (until you switch out), you can pretty much always make use of Mold Breaker because it aids all of your moves, mm will either help against Magic Bounce or some other specific ability like Sturdy Shedinja or Fur Coat.
I assume this Transform feature can also be used with the Ultranecrozium-Z because it would gain the moveset of whatever Pokémon you Transform into but then have Necrozma-Ultra’s Speed Tier, which means you can outspeed most Pokemon without resorting to the Choice Scarf. Further, since Necrozma-Ultra has strong and equally powerful offenses, and a helpful Nueroforce ability, it can be a check to sweepers.
Plus, as it shows that Ditto used a Z-move, Necrozma-Ultra can take advantage of Photon Geyser, and use Light That Burns the Sky as many Pokémon carry Photon Geyser (Dusk-Mane, MMX, MMY, Etc.) letting you even Signature Z-move off of their moveset- since Ultra transforming makes you the species you were assigned by your Item.
The unique thing about these is that you get 2 movesets, your opponent’s movepool until you Mega and then switch out, and then when you switch back in (having gotten rid of your Imposter ability), your own movepool that can completely compliment the original Ability for that form.
TLDR- are there any good Imposter Base form uses we can have?
Also I forgot to mention that these quotes above mentioned Rayquaza can just have Dragon Ascent and lose the move when it Imposters, but still be able to Mega Evolve, this means that Rayquaza can also gain a new Speed Tier when it Megas and can do so while holding any item like Scarf. Why does this matter? Because most Pokémon that it would copy don’t have 180 Atk and 180 SpA, and Rayquaza regaining its Status. Typing, and Ability could allow for it to be an awesome Choice Scarfer. Or Life Orb User.