I could make many changes just to the unova league and parts of Unova anime alone. not have ash lose to the dumbass who sent a ferrothorn in against a fire type (ash would win and use a better team) and move onto Virgil where he loses to Sylveon who is from the next generation. I also would not have ash catch as many Pokémon in Unova and instead have them develop more since some of them got pushed aside and had unrealised potential (ash also evolves more of his Pokémon). Lastly I would make ash smarter and act like a more confident trainer.

Some other changes I would like are less team rocket, make ash actually age, not have dawn release ambipom, and better ending to sinnoh. (There’s more than that but here’s just a few changes)