This is very unfortunate. Such a mod was availably in-built in TS1. It was a very essential cheat, as I kindly recall. (Additionally, it arguably hardly obstructed game play, which was one of the things I regarded great about it!).
In view of the nature of the world I seriously doubt it's technically possible.
It didn't always make the world map look good (TS1), but nevertheless, the cheat was in fact available.
I would think that the coding in all Sims series, including TS4, would allow for something so fundamental as map_edit. Players used it to great benefit; why shouldn't we be allowed to add more squares, if we needed/wanted to. I realize that TS4 is likely using some very different system than TS1. Regardless, it should be made available as a cheat; because people need it.
Anyways, thank you both for your answers. I appreciate it.