1. More transport options (e.g. ships), and the option to travel on these, and existing means of transport, in real-time -- perhaps with the option to 'wait' to speed up the trip.
2. More companions/followers, with more diversity in class, gender, and race. There's only one Nightblade-type companion in the game right now, for instance, with most others being warriors or archers, with a few pure mages. Need more: spellswords, agents, witch-hunters, necromancers, etc.
3. A companion command wheel, a-la New Vegas.
4. Vampire and werewolf questlines, a-la Morrowind/Bloodmoon.
5. More hairstyles, and the availability of dreadlocks for other races than the Redguard

6. Additional, more powerful food recipes. I know the developers wanted to balance food creation so that it didn't outdo alchemy, but it might be nice to have a few more recipes with super-rare/hard to obtain ingredients which provide special bonuses of some sort.
7. Unarmed... 'nuff said.
7. ... basically, more of all the great stuff this game already offers

As for what new adventures might be offered up, I'm sure that whatever Bethesda is cooking up is going to be more interesting than anything I could suggest, but I sure would like to get a glimpse of Morrowind...