What Nation/landmass/Gods realm? What races would be playable? When would you want it after oblivion before the fall of the dwarves?
I will let you decide with so many juicy possibilities I can't help but post to hear replies.
Examples play as dwarf up to fall and dissapearance of their race. Or Dremora fighting jyggalag aiding other daedric princes to seal him away.
please be serious that is all.
PS its all hypothetical.
Wrong forum.

And, we already have 2 official threads for speculation about the new TES game, and suggestions.
http://www.gamesas.com/bgsforums/index.php?showtopic=1078674 is the official speculation thread.
http://www.gamesas.com/bgsforums/index.php?showtopic=1080894 is the official suggestion thread.
I suggest using those.