The original mod actually had an example mod doing something similar - although it didn't help that it was by far the ugliest map in the pack.
If you grab the mod from
http://qexpo.quakedev.com/booth.php?id=32&page=113
and load the "desert" map, you can see the effect. Instead of walls in a large room, you can see randomly generated roads being placed in a fixed desert map. But the idea of bounding the playing area with a fixed space is the same.
on lifts: I actually wanted to make a tile in the space set which was multi-floored, with a lift going between the two. You can already attach entities to a tile; I just dithered over doing a lift. All the qc source was written from scratch, and I wasn't sure about starting to include original progs code just to get the lift working. So it never made the cut...