WOuld be cool if a mod or mutator was added where a team player ends up becoming the enemy in an invasion game. Perhaps during the game, a monster somehow curses or somehow changes the player to become a killer of other players, and the other players must kill him. Perhaps the mod or the monster ability to do this could be called "traitor" or something. Maybe the player becomes 1.5 scale larger to show that they have become an enemy.