My next grand theft auto would be somewhere in the middle east, more specifically Lebanon.
Not only because it's my country or anything, but seriously if anyone came to here they would understand why.
You can have the beach, mountains, small neighborhoods, tall buildings, so on.
Now for the idea, it would be a certain patriotic civilian, who got his parents killed during civil war (the Lebanese civil war) and wants revenge from the people who killed them. [ ok the idea is not so much of a stunner but what the hell, it could be catchy.]
A new type of gaming would born, the militia type; it's the gang situation taking up a notch.
Now to talk a little about the main character, I just had an idea of having two characters, and within the game you could change (something like that) but let's not just base our theory on that.
Cars, would be a wide range, from SUVs, ATVs, Planes, Cars, Bikes, Motorbikes & much more.
Weaponry, adding some features to the old weapons (silencer, a knife to the rifle..)