I got this idea after i began building vaults under earth. if you could make a plugin which rewrote all Blocks at top to be remade as sand or sandstone to make a Wasteland Look-a-like world. also if ppl then get slowly hurt when they are up on the surface in that way ppl is forced to live in the Vaults. ... Yes yes i know i just could go play some Fallout. But hey that ain't Multiplayer. Thank you beforehand.
...and I'm most certain WorldEdit can replace blocks in an area, so you could use that to replace blocks with sand or sandstone or whatever you wanted in a massive radius and optionally use a plugin that blocks people from going out of the boundaries. It won't be able to do it in real time, but hey, it's something.