In the anime, characters use lower-stage Pokemon often. Think of Ash's Pikachu or Qwilava, or of Iris' Axew. Yet there is no incentive for that in the games, as using lower-stage Pokemon puts you at a huge disadvantage generally.

Should future generations change that up so that players can battle with their favourite mon's, even if they're basic or first stage? Not that players should fear a Pawniard the same as they should a Bisharp, but something to build upon "using your favourites".