Well, here's my suggestion.
Add a two-people hotseat mode to Riftrunner. I think the story with the two characters is virtually begging for it. A Network mode would be much work, but a hotseat mode could be managable.
Restrict the area the two characters can move in to screen size (no splitscreen), and leave the rest untouched. Possibly some of the quests would need editing (e.g. if the two characters do something simultaneously, but aren't supposed to), but other than that, I see no problems.
If changing the quests for hotseat mode is too much work, then allow a hotseat exclusive in the random dungeons (hack'n'slash only, a la gauntlet). A story mode would be better, but seeing that almost no game has hotseat nowadays, I would be happy to see anything at all.
One would need to have two mice to play, but if a friend comes along to play, he can bring his mouse, so no problem.
