I always wanted (by always I mean since about 6 months ago when I thought of it) some more strategic magic. In Oblivion you would just put on your buffs and pick your favorite "does every kind of damage" spell, then pick your favorite sword to slash with. After playing the recent Fallouts, I thought of something VATS-ish for some spells.
Take your average "magic missile" type spell. Now add a lock-on feature of sorts. Now you can queue up 2 or more of each spell to occur at once, to take care of multiple enemies, if an area effect spell wouldn't be enough, at the same time. Something like that at least. Definitely extra cost to magicka for simultaneous casting, but being able to cast five magic missiles at once would make me very happy
Also, location damage. Maybe not for spells, but definitely for physical weapons. Maybe even add gore (since it would make sense, I'm not just trying to be nasty), where you could chop off a living creature's leg, forcing them to crawl to you. I know, it's nasty, but crippling a minotaur in such a fashion would certainly make it easier to kill, since I hope that they make monsters like that much harder to kill.
For archery, bring back crossbows. This game takes place over a hundred years after Oblivion right? And I know they nixed crossbows for Oblivion because of the simplified math in the combat system or something. But really, it would do more damage overall, especially to unarmored or lightly armored (chain-mail) enemies, and take much longer to load. Balance, I suspect. Also, nobody uses archery enough to make it level up fast enough. Or, at least, I didn't. I would sneak around in dungeons with my bow, sneak attack somebody, then take out my sword because I knew there was no way in hell I could ever attack with a bow at point-blank range. As handy as it was, it never leveled up fast enough for me. Make it go a bit faster, would be another of my requests.