Possible future candidate for an adventure map
From my point of view, creating a tool, that would perform your desired action efficiently, is often better than just doing mentioned thing.
In last few days I've developed a small tool that translates given commands into series of WorldEdit plugin commands, and provides simple interface for writing dynamic scripts that modify world contents, even without having access to server to be able to import JS scripts.
Since game handles input nicely, a single message can be sent every 200..300ms, meaning that subset of commands needed to change selection bounds and perform desired operation over it often takes less than a second to perform, in comparison to minute-measured time needed to do same manually.
This opens rather interesting perspectives of automating creation of typical structures, as well as making it possible to push procedurally generated content into game easily.
Yesterday I've spent some time to port part of RPG05's dungeon generator for use with this, and this is the result.