A huge invisible interior (like slate, except you would make your own, preferably). People may occasionally fly or ski through it but it's about the best you can do.What do you specifically need it for?
Isn't there an onExitMissionArea function or something for players? You could use that to respawn them or show "get back inside" messages with a package when you open the map, deactivated when you leave.
you got to declare where the points are and stuff, i don't know how but you could look at one of MtnDew's map cause it had something like that if they aren't in a vehicle.But, are you gonna release this cause it looks cool.
Yeah, texture it in a texture called null.jpg and torque should automatically make it invisible.