Don't base it in just one province maybe start out with 2 and then release expansions that add more provinces to the game. Hopefully ending with the player being able to travel to all the known areas of Tamriel.
More armor types and weapon types.
Better enchanting system.
More humour.
Better Alchemy system.
Better Construction Set.
A built in mod manager where you can change the load order etc. You must provide for all audiences including the modders and non-modders.
More attention to detail, what sets this game apart from others is its great attention to detail, I would like to see much more of it.
Better leveling system for skills etc.
More varied voices for NPC's.
The ability to ask people their names or find out from others. Until you find out they are just known as '???' or if they are a guard or another role which can be identified by their armor they are just 'Imperial Legion Guard' (or whatever else they would be called).
More Unique Landscapes, I don't know if you took a look at the Unique Landscape mods for Oblivion but they were fantastic and made the world feel so much more real instead of every place being a carbon copy of the previous one that was just slightly edited.
Better Magic System.
More spell effects.
More spell textures and stuff I can't describe it but I hate how when you cast every spell that has a fire effect and fire only they all look the same. It would be great if they were more dynamic and the better the efffect the bigger the fireball or something.
Maybe an ability for spells to jump from one person to another.
Also more magicka, or less required for spells, even when I had awesome armor, was a high elf with the mage class and the wizard birthsign I could still not cast 'Fingers of the Mountain' (level 30 version) more than twice, 3 at maximum.
More wildlife and insects, bugs etc.
More customization for houses etc.
The ability to buy certain houses or kill the owners and seize them for yourself.
The ability to have people fear you and love you eg, you break the law but the guards are so scared of you that they don't attack.. unless their is a guard captain with them that boosts their morale which brings me to my next point...
Morale, certain NPC's should boost morale for nearby NPC's eg, Guard captains boost the morale for guards.
No leveled items on bandits and stuff, getting to level 30 and having every bandit have a full set of glass and daedric armour was just stupid.
Open Cities, this is in reference to the mod 'Open Cities' that opened all of the cities up.
Having Open Cities would allow dragons and other cool flying mounts, seeing as how you could see everything from above and just go land there. However keep the cells for interiors that you have no way of seeing or getting inside without teleporting to the interior.
Travelling people, more NPC's travelling between cities.
More people in dungeons.
More varied cities.
The ability to become count/countess of maybe at least 1 or 2 cities per province.
The ability to become King, not Emperor as the player would have to be from the bloodline, which brings me onto...
Maybe they can be from the royal bloodline but they were illegitimate and was therefore cast out as a baby... just an idea for a new main quest, hint hint.
Better combat system. Slash, Slash, Slashing with the sword gets old quick.
A hardcoe mode where there is no fast travel and players must take carriages (which travel between the cities and the player can raid them etc) or hide in a trade caravan (which players can also raid).
A 'postage' system, so I mean that information takes a LONG time to get around for example you could become king in Cyrodiil but people in Morrowind or Vvardenfell won't know for about a month, unless you take it upon yourself to spread rumours.
The ability to spread rumours, make people pay for YOUR information.
Better AI and graphics goes without saying but... just incase... Better AI and graphics please
That's all I can think of at the moment I'll add more when I think of it.