I just recently watched a video on the evolution of Pokemon battle animations in the mainline games.
Here's the link if you are interested, it's pretty amazing how battle animations, subtle or not, evolved over each game, let alone each generation:
Considering the ever-increasing list of Pokemon (over 800 and counting), the time and development in HD games, the almost yearly iterations, and other aspects in the main line games, what would you like to see as a change in the battle animations?
I agree with the video in that a little more animation from the various Pokemon (outside of Pikachu and, recently, Eevee) would give the various species their own unique personality. And maybe a little tweaks in some of the attack animations that fit with the Pokemon's physical features would be a good change as well.