Few things:
-A.I. Adaptation. Meaning if i shoot you with an arrow, You learn to dodge instead of continuing to run straight at me.

-Damage realism. I really hope they've worked on this as much as they've said they have. I don't want to turn your face into a pincushion with arrows and have you still failing your sword at my face. A fallout style i guess. Arrow in the leg enough you're not gonna be walking very fast.

-BETTER THIEVERY SYSTEM. I think i speak for a TON of people when i say, Pickpocketing, Stealing items that somehow people don't EVER want to replace, And only being able to sell them if you're in the thieves guild... Lame. What if i want to be an independent thief? Or what if i want to plan my own ultimate heist? I want to be able to do that and a ton more.

-Making my own 'Guild'. I don't know why that hasn't been thought of. I'm a hero, Why can't i make my own guild called the badasses and maybe we can either decide to pillage your village or on a good day, Kill you. I'd be happy with a simple set-up with that. Name: BAMF Clan. Recruit Role: Get Info. Member Role: Start to steal what we may find useful. Trusted Member: Able to join planned events by lieutenants. Lieutenant role: Plan village raids, Dungeon Raids, Assassination missions. Captains: Dealing with allies (IN this case probably the moran tong or dark brotherhood). Leader(You): Able to do all those things, Promote/Demote members as seen fit, Plan attacks or sabotage enemy factions.

Like yunno, Just kinda give you a list of how many ranks you'd want. Then from that, A list of what each rank could be set to do. Script certain movements, Actions and whatever else is needed to get those pre-set actions to work. Such as for getting info role of a recruit, He'd walk around towns talking to people, Becoming friends with people, And asking if they know anything of importance. Not that hard. The recruiting wouldn't be to hard either, I mean each NPC has a set attribute and skill rank anyways, So if you get to know someone you can start being able to ask him/her to join you in creating this guild. Then he/she can recruit people they know and so on. The planning raids might be a bit tricky but I'd view it as an npc giving out a quest to go get something. The game engine would assess the skills of the people wanting to participate, Calculate which monsters should be in which dungeon and what loot would be of equal value to the danger faced. Assassinations and stuff like that i guess could be the level of difficulty to reach target, Protection of target, Ect.

Edit: Just to clarify the beginning of that last part there, What i meant by a list and pre-set actions. The list's could go something like. You get a 'Rank' menu, It would give you an option to choose however many ranks from I'd say 5-10. Next menu would be an 'Action' menu. In this menu you would be able to choose from pre-set actions you would want you're Guild Members doing at that rank. I've already gone over some examples of those such as Stealing, Info gathering, Ect.

I kinda went off into detail but that'd be friggin AWESOME.

Large scale battles that aren't broken and buggy.

Spears