After you defeat Lord Harkon in the cathedral, it would've been nice to be able to roam Skyrim turning hapless humans to your ranks. (And after they turned, you could use them as a follower.) It also would've been great to be able to fly upwards instead of just being a foot above ground level. Could you imagine how much more epic the dragon battles would be? What kind of abilities or quests (For vamps) would you liked to have seen?