I have no idea if this is possible to implement on the client side, but it would be really cool to be able to pick which subbed communities are emphasized or de-emphasized in your feed.
For example if you're on a niche sub that only gets a few posts per week, maybe you want to ALWAYS see new content regardless of how many upvotes or comments it gets.
Conversely, I enjoy a few meme subs, but right now Risa completely dominates new/hot/best filtering for me. I'd be perfectly happy just seeing the top few posts sprinkled throughout my feed.