seems to be quite similar to what can be done using Baker's undergate map pack.
http://quakeone.com/files/2-maps/8-undergate-release-2-7-zip/
This pack comes with a launcher map, or a hub of some sort, via which you can easily access all the maps in the pack (mostly the hall of fame maps as rated in the now defunct Underworld Reviews site)
One catch, though, is that the hub map doesn't randomize the accessible maps. You need to manually pick which one map you want to play. Though this can be "randomized" by closing your eyes and walking blindly in the map, until you stumble into one of the teleporters leading to a map.