The Golden Mask and the cape you get in sequence 9, and a new armor set that like the Missaglias armor but indestructible like Altair's armor, Some new weapons of course that would include a maxed out Florentine like falchion sword.
I'd want some mission where you were swarmed with enemies. Even a hundred plus... Make it hard, this game overall the combat is too easy because you're such a bada**. Some type of gauntlet of mission where its near impossible to win.
Also... Some more info on that "dream" sequence...
Also... it would be really cool to play through some more missions as Altair in either old cities like Acre or...
-- new "co-cities" where you alternate between both Altair and Ezio (this would be more of a topic for AC3+)
I'd love more outfits (not cloaks, but full outfits - like the Uplay Altair one). Like being able to get Ezio's starter clothes as one, or being able to play as other characters, appearance wise, such as Mario, Giovanni, Rosa, etc. In general I'd love if they gave a female to play as, even if only visually when just running around doing random stuff.
Ooh, and the ability to remove all armour. I like how we can switch back and forth between the different sets, but I'd love to be able to remove armour entirely too. *Nods*
As for more mission-like-DLC, I think a series of mission during the 'Ezio you're now an assassin!' and then the 'jumping back to him ten years later' time period would be nice. Doing tasks and having conversations with each of the assassins, maybe learning new combat tricks and such?