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Something I noticed:
In SV, Arceus actually has unique icon sprites for its forms now. It might be worth it to reflect this on Showdown.
The PokeSprite repository has good custom pixel ones.
There's apparently a Sheer Force flag, but its not on all moves that are affected by Sheer Force. DaWoblefet said above that it affected Order Up but it didn't remove the secondary effect, which caught my eye since that was one of the moves that had the SheerForce flag.
Perhaps the flag sets...
Bulbapedia says Instruct cannot be used while the target is in the middle of Bide. Is this true? Showdown currently doesn't simulate this, which is why I'm wondering.
I think the best way to go about this is by treating the same pokemon but from different gens as different forms, with different sets and strategies. That way we can ban Mewtwo-1 (first gen mewtwo) from OU if it's too powerful with its uncapped EVs just like you would any other powerful Uber...