If they upgraded the co-op, I think that would be the best. Hell, if the only thing they did for the co-op was make it so each player had their own camera I would be happy. Because then co-op wouldn't COMPLETELY SUCK.
Also if they made a hard mode. Seriously, I've heard of people (Yahtzee included) talking about dying in the game. I wouldn't have any idea what that like, I never even came close to dying. In 2 complete playthoughs of the game I've only used 1 Res. Phial. If anyone is wondering where it was when I fast traveled to Brightwood Tower after rescuing Garth. Seriously you get swarmed by like 50 spire guards and those tougher ones that can cast those really annoying spells. But since I showed up with something like 22 Res. Phials, I wasn't worried.
Anywho... It'll probably be DLC. New clothes (including a fancy new hat!) and maybe some new weapons. New Legendary weapons would be nice. Since all the legendary weapons in the game, except the Daichi and the Rammer and I guess the Enforcer, SUCK. Master weapons with some decent augments you can buy at the market are better than all the other legendary crap you find.
This is long now...
/post