3) More/more interesting and useful spells. Especially in destruction. I really only resort to spamming firebolt/fireball which gets tedious.
2) Some Epic plotlines. I felt that the Dark Brotherhood questline was awesome, but the other guild/MQ lines were kinda straightforward. Would like to see a DLC with a large overarching quest line.
As long as this "epic plotline" is not like Knights of the Nine. I hated that DLC - mostly because of the possibility of ruining my character. If I join the Dark Brotherhood or Thieves Guild, I don't want to be some stupid goody-two-shoes knight.
If anything, DLC needs to stay away from junk like New Vegas (where it adds all these new "stay until you're finished" quests) and just add things that enhance the game that is already there. New items, new quests, maybe more land to explore (without constraints), new perks or skills - things like that. The "main quest" in a DLC needs to be isolated from everything else, and started only by the player. I want to visit High Rock or Hammerfell and explore at my leisure, not be thrust into some quest line I can't leave. The DLC needs to be like what Skyrim is right now - completely open ended and ambiguous. I would actually prefer they stay away from super-stories and just add a bunch of smaller content to enhance the world, or fix/add to things that are already there. Expansions on the guilds with more quests, some sense of "rank" and introduction of other guilds (like the fighters guild and mages guild, which would be separate from what's in the game now).