Set in Morrowind. Preferrably play a nobody, I'm tired of this "you are a wizard, Harry" bullshit Bethesda uses in every. single. game.
Set in the Red Year, before, middle, and aftermath. Could possibly meet the Nerevarine in the beginning of the game, who knows.
Better quests and questlines. None of that "fetch that potion from the house down the road", none of that "master of every guild". I mean, The Witcher 1 makes perfect sense for me because you are a Witcher, you kill shit people are too afraid to kill/can't kill, and I don't remember any single quest so far (around 20 hours into the game) that told me to fetch items that didn't have at least a plausible explanation as to why I had to be the guy to fetch those.
In Skyrim it feels like you are the region's courier. You and you alone are the only person capable of transporting goods from point A to point B, no matter if it is as big as an entire region or as small as house 1 to house 2 in the same town.
That said, it would be nice if at least the fetch quests were timed. If you refuse to complete one, eventually you will return and the NPC would say "I already got someone to do it for me". Otherwise, the world feels extremely dead and artificial.
I would love to have a world that's much more believable. Better NPC schedules and interactions. Inns tended to by multiple NPCs instead of the same old "I'm awake 24 hours, what can I get you?". No more recycled dialogue all the time, NO "WE'VE GOT WARM FOODS, WARM BEDS AND WARM DRINKS".
Make guards shut the fuck up, or only say things that make sense for them to say. You don't see police men greeting you with stupid shit in real life, why should every Guard devote his attention to me? More over, Guards keep the peace but you never, ever, see guards do anything in Skyrim. Morrowind has the small exception of you drawing wild beasts into town, so the Guards take care of them. But in Skyrim, the only troublemaker is you and you alone.