http://www.pokecommunity.com/showthread.php?t=212492
As you can see in this thread, it's very difficult to being near impossible to add the amount of map names you would need to include every single region. Not to mention, that's a huge undertaking even if it were possible simply from a time and motivation viewpoint. I would particularly discourage trying something so ambitious if you've never even made a hack before, and I mean that in the nicest way possible: start small, learn what you can and can't do, and then gradually add more and more stuff.
That way, you constantly have new content you can add as your skills increase and you aren't left repeatedly disappointed at the outcome.
Alternatively, you could turn to game development, as opposed to ROM hacking, and create this multi-region Pokémon game in RPG Maker, though I'd still advise against it.