More customization of my Pokémon
Do you know what’s really lame about Pokémon? The fact that my Pikachu isn’t any different than your Pikachu. I mean there might be a minor difference in stats and maybe one or two moves, but they aren’t all that different. And that doesn’t make a whole lot of sense. These are Pokémon raised by different trainers who have had different experiences, and you should be able to reflect that in a manner of ways.
Maybe when a creature levels up, you have the option of choosing what stats increase as you do in so many other role-playing games, but a simpler and more fun way to do it would be fun and colorful accessories your team could wear. Headgear, scarves, shoes, collars, luchador masks, whatever. Something that makes your Pokémon look fairly unique and also maybe provides stat boosts but honestly the more important thing is making it something that doesn’t look like most or possibly anybody else’s creaturees.
It might even give you a good reason to have more than one of a particular Pokémon just because their accessories make them different enough to have a different strategy in battle. They played around with this idea just a little bit in the Pokémon Let’s Go games, but I would like to see the idea more fully explored, even if it’s just for cosmetic purposes, in Sword and Shield.