After that I'd always wanted to make a quest. Something long and rewarding. With voice acting. There's too many quest mods that arn't voice acted, and for me, that's a no-go.
As for what I hope they add into it, the ability to change body meshes and skeletons per race and gender would be good, although I think I read that they're doing that, at least for the former. It would be even better if you could change those things per person. I imagine there will be mods along the lines of http://www.tesnexus.com/downloads/file.php?id=16843 that also things like posture, adding to each NPC's individual personality.