Who would you like to see make an appearence again? How would they have made it to the present (ghost, time travel etc.) And what would their role be?
Personally I would like to see Crassius Curio from Morrowind. A ghost who wishes for nothing more than his famous work to be made into a play. I can picture quite the hilarious quest and interactions with him.

Count Janus Hassildor still living? A new spin, perhaps the count in rags, met on the run from The Vigilants.

Divyath Fyr. Badass Telvanni Wizard who is thousands of years old? Yes please.

Yeah, I'd say Hassildor, considering he was an interesting vampire, and the new DLC is all about vamps, I think he would fit in nicely. I'm hopeing at least he will be some sort of easter egg, like sinderion for that crimson nirnroot quest.

Yeah I liked the Sinderion Sarethi content, maybe the count could become a sidekick through a dlc.

Lucien Lachance. I mean actually him...

Lucien LaChance or Vicente Valtieri

Damn you beat me to it

Emusette Bracques in Morrowind for only giving me like 3 health potions and some disposition for helping her friend.

I can just see how many 'daughters' Divyath Fyr would have by now lol