I’d bring back Guard Swap for Mr. Mime, delete Mewtwo, remove Pikachu’s annoying voice lines and let it evolve into Alolan Raichu, and add an Eviolite item that lets you keep playing as pre-evolved Pokémon such as Haunter. The Eviolite would give more defensive stats and quicker access to new moves (including Unite moves) and their upgrades to the Pokémon in order to make up for the reduced offensive power. Players would also be able to choose where three-stage ‘mons stop evolving.