In my mind there are two things that would be MAJOR improvements to this game, and make it feel much more complete.
1) Player housing. One of the biggest features in TES games is being able to collect things and display them in my house. It's a shame that TESO won't have player housing at launch (or in the near future), because it really would have made things feel more TES. Keeping epic loot on mannequins, books on shelves, ingredients in chests, etc would really make it feel like TES, and wouldn't be that hard to implement at all, just a private instance with "bank" like containers where your loot doesn't disappear. Would this honestly be hard to make? No. They took the time to make a player bank (where banks have never been seen in a TES game), but not just make a player house? Seems like a big mistake.
2) More interactive "auto" combat. Since most damage in this game comes from the auto attack like in past TES games, I feel like auto attacking should have more options besides light and heavy attacks. A combat system like in Kingdom of Amalur: Reckoning would have been perfect. Normal heavy/light attack system, but with several other options to spice it up. Skill trees could have made these particular attacks more deadly or useful too.
Just my 2 cents for the night. More interactive action based combat would be nice, but isn't a deal breaker at all. I really think it's a terrible sin launching a TES MMO without player housing though, and considering we won't be seeing anything like that for a year (at minumum, probably longer or never) it's a big downer.