Possibly the return of the class system. I love Skyrim's skill system, but I didn't realize this until I played oblivion again a week ago. But Skyrim tends to set you off with a pretty bland character as far as skills go. And unless you're playing a straight up warrior, sometimes it can take a couple hours until you actually feel like the class you want to emulate. While in Oblivion it starts you out with a decent start in the skills of the class you selected (or your own custom class). Which helps significantly in getting the ball rolling for your playthrough. Of course Bethesda would have to strike balance between the two of course so that it wouldn't limit player creativity. But I feel the return of the class system, so long as not limiting, would help with immersion as well as RP and the general flow of your character development. Also... throwing weapons and cloaks (Seriously, I want to play a caped knife thrower on my console).

Thieves guild for sure.

Breton, then Dunmer, and Bosmer last. But I also play around a bit with Khajiit and Argonian from time to time.

Witchhunter, by far my favorite class in the elder scrolls series.

Nailed it! I him The cleric.