You know, this popped into my head while talking about Summerset and its lack of any new classes (that I know of).
Why not an expansion like 'Oblivion Wars' where all the Daedric Lords are at war, upsetting Oblivion and thus Nirn in some way.
Add classes whos looks (armor, tattoos, weapons) and skills and fighting styles are based off of each Daedric Lords personality, and add all of Oblivion as a new world map to explore, with PvP zones to further ones Lord's power, and the whole storyline is to try to STOP the fighting and bring balance back to Oblivion.