I would like to have an evil race. Much like Dremora to be something you can choose or something similar that is a dark and evil race. I had a lot of fun with this race through mods unlocking it playing as a dark mage.
As for a new guild, I would love it if they made a variation of the mage's guild to be split up into sections for alchemist's, scroll-maker's, demonologist's and pure magics.