I've been playing around in MCedit, you can do a lot of stuff in that program
. I always thought it would be complicated to use but while testing I copied the entire Exoddus settlement to a completely different world in less than 5 minutes.
In the future I might use it to stitch all current worlds together (like Dark suggested a while ago, I think). Right now it's quite messy with the seperate worlds and stuff (that and I'm not sure if The End works properly if you manage to get there from Ma'spa). Only downside would be different biomes around Genesis and Exoddus. But we'll cross that bridge when we come to it, it's not something critical. Fun program in any case.