/u/StezzerLolz suggested we could drop a random dungeon onto a map. Development discussion at http://www.reddit.com/r/rdgfilter
I used FILLTER to block in the exterior of a simple set of cubic volume 'rooms', saved it to a file in the "DungeonSchematics" subdirectory off filters, then ran the script. It works.
What would be good is to have a way to paste into the underground without the schematic overwriting the blocks already there, except where the rooms are. I guess it depends on the dungeon design and this is why they are normally procedurally generated. I might set it up randomly with linked rooms instead. Anyway, enough for now.
Two dungeons are hidden near the surface of this map:
What my test schematic looks like:
MCEdit Filters >