I also want to get rid of "notifications" and replace it with something that isn't a Pavlov's Bell. I'd like to track replies in their own conversation interface. Boosts and faves don't need individual notices, and could probably just be replaced with a tab for seeing which of my posts are making the rounds.
I want to make the bookmarks feature more robust, and I'd like to keep an offline cache of posts I've seen so I can search them easier.