I say you might want to get rid of the glitch where you can shoot through the boxes on corridor. its unfair and very difficult to play it when people do that
i would reccomend putting in some sort of multiplayer co-op missions. this way if you complete the mission based on how hard it is, you get a reward. like 5 gold for an easy one and maybe 20 gold and one cash for an extremely hard one. just an idea :p