I really like the idea of big packs similar to the mass marking/item packs. Like having packs of a ton of user-created objects all included into a few groups in order to make things more organized. Could even be done with emotes and such. I've wanted to do it myself, but it's a bit of a big project to take on, to try and get permission from all these different object makers, a lot of which are inactive. But if someone were ambitious enough to take it on and be able to organize things neatly and credit everyone properly, I'd love to see that.
On a smaller scale, I'd love to see more love given to some of the more unpopular types of mods, like free heightmaps, mask mods, and terrain textures (honestly, I have no clue where half the terrain textures I have came from. There's not many terrain texture packs out there, yet I've just accumulated a ton of them). Free fur textures are always nice to see too.