Yes, room deathmatch would be an awesome idea. Everyone is a shamman and it's a fight till the death. If this ever does get made, though, there should be a limit of 10 or 15 mice per room, so people don't lag out from all the spawning.
Silverclue. Great thought, but there's one flaw. What if you keep on killing yourself to create lag? And, also, you'd get in the way if cannonballs and other sham objects. And if you say, "No, you could be a ghost." then how do you walk on them to 'test them out?'
You shouldn't be able to move potions, monsters, ect. But you SHOULD be able to customise waht kind of monster you're fighting, or what kind of potion you're drinking.