Well, considering the books take place between IV and V there's kind of a large span of time there, so the human races would probably all be dead.
I'd like to see references to older characters and family lines, but I can't think of any characters that would feasably still be alive that i actually want to see.
Except Divayth Fyr maybe. Here's hoping he didn't die when Morrowind got bowled over.
I'm sorry, but are we sure of the timeframe?
It could very much be immediatley after Oblivion, or during the events of the Infernal City. I did not read the books, but from what I know of lore, the Infernal City does not reach Skyrim. It could very much just be an event happening at the same time, and we would hear of it from rumors and such. Perhaps it could even play a minor quest role. That is, if its that far after the events of Oblivion.
M'aiq is a must of course, and I wouldnt see why he wouldnt be in the game to make fun of the forums complaints.
Considering you are the Nerevarine in a way, I couldnt see him being in this, for you controlled who he/she was and looked like. Same goes for Sheograth, I suppose?
A dwemer of any kind please, I find them extremely interesting and would love to know why they dissapeared.