I don't know about how demanding dimensions are for the server... I just got the idea that you can maybe sell books to staff-made void-worlds (keeping up the ban of the regular Mystcraft). The idea behind it: A void world is more lag-free (I guess) than a regular one. Maybe some people want to build their base or some machines that would cause lag in the regular world in a void world.
they did something like this, t5 donors ONLY could make/use mystcraft worlds on monster, then again monster had it's own 5 servers...