Would it be possible for the mods to add sub categories that allow for more than 2 players for co-op?

depends on what kind of sub-category you'd prefer i guess. i think it still needs some of the other mods' opinions first. i personally have not much problem with that tho.

Sorry for the late reply, how many players are we talking about here? The game is not quite stable in multiplayer which was one of the reasons why ILs were limited to 2 players and full game to 4.