Best thing is that you can even dream of creating campaigns for other DM to run. Just like the real thing. After all, at the core of almost every campaign, there are pre-established maps.
The ultimate trick would probably be to let your player start on a small patch of land into the nothingness and build the world as they go, which would be some X-trem GMing. If the tool work, however, I can almost fully expect that someone will try it and suceed at it. Modders are a rare breed of passionate people.