Found the
EpizZones plugin which allows zone-based mob spawning (and a bunch of other stuff).
So if there are any scaredy-cats still wanting to play we can have a safe "civilized" area, but still have monsters enabled in general so the game is more interesting.
Also provides a list of multi-world plugins, meaning we could provide in-game switching between the existing map and a new one - although that implies the ability to carry inventory, and personally I'd prefer a completely fresh map, without any imported goods.
:PEDITED: 18 Dec 2011 20:36 by BOUGHTONP