Playing the Prequels (except SR3) with a shortened story where you don't have to reearn respect and keep your SR4 weapons&upgrades.
If you want SR2 with wilder weapons and an option not to have to earn respect points between every mission,
this should do the trick. Just be sure to select "open respect" on the build-your-own submenu.
As for what I'd like to see in future DLC, here's a short list:
*all super homie outfits available to the player
*some 40k weapon skins (bolter, chainsword, that kind of thing)
*additional songs for the radio stations (actually, this could be a great way to handle the "songs are too expensive to license" issue: just offer the artist a cut of each sale like what iTunes does)
EDIT: almost forgot a couple
*the shark gun (possible spoiler:
we know from one of the missions that the "shark popping out of the ground and eating someone" animation is still in game, so this shouldn't be too hard to do)
*more homies from past games (especially Jenny, Tobias, and Laura)