I nearly didn't try this game because of all the negative reviews and plain hate it got. I am happy I did because I am enjoying myself but I am still feeling trepidation about end game.
Here's what I think would nail this game out of the park.
Player Estates... No not player houses or player keeps or even guild keeps but versatile player properties. The reason why I want to see this is because it would do soooo much for the Elder Scroll choose your own adventure motif.
With a player Estate, whether you execute an NPC... pull them back from Oblivion or what have you; this could all have meaning. You should be able to acquire property in 1 (yes just 1... the whole Vet replay aspect is an ill conceived child to begin with) of the alliances and future content should build on this idea... take inspiration from games like Suikoden... NWN2...
The next thing I want to see is ZeniBeth being brave with skill lines. The classes they put in are totally arbitrary with little to connect them with ES lore. This is good and bad. It is bad because it doesn't sit well in the traditional ES framework, but is good because it is easy to salvage and continue to add too.
I want to see added skill lines to further define player options that tie directly to the franchise. BRING BACK SCHOOLS OF MAGICKA... They would be great for adding more out of combat utility. Also, bring specific weapon type lines that synergize with the 'weapon style' lines already in place and further refine choices... skills and passives that specifically drawn from a maces/mauls/axes line for example. And as you expand the game, add more new skills than you give skill points to players. This way there is a huge incentive to make more than just a few characters that have EVERY skill.