For an existing save, it may be easier to enable 4 players by hex editing one of the game files. See the topic
Multiplayer mod (if you make a backup of the file first, do so in a different folder, or it can cause the game to crash on startup).
Edit:
Nevermind, it worked. But seriously why hasn't Larian added four player support yet if that's all it takes?
Only thing left, is how can I change (companion Wolfgraff) the 3rd player's name/character image/etc. with MooseEdit?
