I'm p.sure it's actually number of people. 140 seems the safest you kan get, maybe 150, but iDon't think a full 200 man server's going to last long enough to do an event. Kall it superstition, but I've seen lots of explosives and force powers used with nothing going wrong-- also, Warband engine isn't made for Force Powers?
It's also not made for cannons and destructible scenery and rockets and ropes you can swing across as a pirate and fully animated sailing ships (look up YoshiBoy's old mod) and... well you get the idea. Honestly I'm happy the mod's this stable as v0.3.