This is by far the most requested feature by content creators and it's not even remotely close. It would make the process of finding replays way easier than going through every page 1 by 1 clicking every battle. As someone who makes videos for myself Freezai and a few others, finding relevant replays can legitimately take hours. This feature quite literally would save everyone 10's of hours over time, and iirc there was a Pokemon Showdown tweet regarding suggestions for the replay revamp a while back and this was by far the most requested thing (tweet isn't up anymore it looks though).
This is definitely a big want for many casual and competitive players as well who wanna see how a Pokemon is used especially in high ladder (theoretically you can do search by rating + pokemon), something that allows you to search for a Pokemon's replays in a tier is just extremely convenient and for more than just these reasons. I'm really knowledgeable on how the replay search code works yet, so I'm not sure how realistic this would be since I don't know how Pokemon data is tracked, but hopefully it's in the realm of possibility.
This is definitely a big want for many casual and competitive players as well who wanna see how a Pokemon is used especially in high ladder (theoretically you can do search by rating + pokemon), something that allows you to search for a Pokemon's replays in a tier is just extremely convenient and for more than just these reasons. I'm really knowledgeable on how the replay search code works yet, so I'm not sure how realistic this would be since I don't know how Pokemon data is tracked, but hopefully it's in the realm of possibility.