to be honest, i still dont like the idea of an mvp room. geared players can already hunt mvps efficiently, give them another way and they will still rule over the economy. I myself like mvp hunting, i can just hunt an mvp like kiel, after killing it in the real map, i can summon one again if we had mvp room.
but if we ever have to do it, lowered drop rate+ zeny to summon+ limit to summon on each account altogether should work though. mvp drop rates are at 10% normally so something along the lines of 5% and below would be ok.