Hi there, your thread was not accepted because it was largely asking a question about how to make such a hack, which means that it would have been better off in the
Simple Questions thread or even
ROM Hacking Discussions depending on how you chose to phrase your post.
I'll also answer your question here: You might be able to do that in an expanded third generation ROM, but you would definitely need to expand its file size. I'm not 100% sure about the first and second generations, but I would assume that they are already largely full and wouldn't be able to support another region on top of what they already have. The fourth and fifth generations do not have a map editor at this point in time so it is impossible to do it on them in the immediate future.