Too big.
The game would be unplayable, for one. Bethesda would have hell bugtesting it.
ex:Daggerfall.
Daggerfall would have been much better without all the bugs
I think a game spanning 2 or 3 provinces would be fantastic.
And Summerset Isles as a travelable location, similiar to the Tribunal expansion to Morrowind, seeing as Summerset Isle is literally a giant city on the ocean