World Merging Help

Hey there guys so I have a server and need help, I would like to merge my other creations into that world, but without mcedit. Because MCEdit makes quite a big mess and I have quite a big city, so therefore I would like to merge that world with one.

I dont want a portal to go to that world btw, I want it to be in one with out having to do /warp or /tp or /portal.

Someone please help me