Obviously it's hard to tell with the info we've got in hand but I have the feeling that companies will be the answer to most of the points that you proposed (intercity rivalry, city missions, associated dungeons and town defense). And the devs have stated that there will be a fame system. Airships, chocobos, we know they are coming.

So yeah I think future adjustments to the game will help spread people around, but I'm not sure that adding restrictions to current players habits is the good idea to provide this spread, like in some ideas that you posted.