Hmm, I'm slightly afraid that most players will choose the Southmont region, putting a certain similiarty in play styles and cities. On the other hand, the players of the game who've actually seen this and not a cavalry post (later on) that expands upon it's bonuses will be in the minority. After all, I'm only choosing Southmont because I live in a pretty flat area, and as such am always amazed if I ever visit a mountanous region. It strikes me as nice to think that I'll be able to see that sort of scenery every day if I make my city there.
Also, my rts play style is fairly turtilish. It's probably because I fail at multi-tasking, and need walls to protect everything for me
In regards to GPS, I'd hope we wouldn't be able to use Postern gates as a way in. Not only is it un-realistic (people don't design open doors into fortresses) it'd be unbalancing because people could bypass both wall and gates easily, even if they are hard to find. My final argument against it is that they've never shown an AI/themselve taking advantage of them. Unless it's going to be this game's best-kept secret strategically, I don't see it being implemented.