Vexa

I'm thinking this DLC would involve the Thalmor, maybe quests leading up to the Thalmor being dispelled from Skyrim?

Yes, everything belongs to you. And yes, you can put your stuff in all of the containers in his room.

Awww, I thought this would be a fiery explosion. Still cool though.

In you case, I would say go with smithing and enchanting. I don't see the need in robes or light armor, to be honest. Just disenchant the robes with enchantments and put the enchantments you got on heavy armor if you're going for the Battle-Mage type of thing. Oh and don't worry, there are PLENTY of quests in Skyrim, you won't be finishing the game anytime soon. Plus, there are plenty of mods to keep you satisfied even if you've finished the game.