Quote Originally Posted by Kaedan94 View Post
There are no invisible boundaries in the new areas except for the actual edge of the map. There's nothing about the old maps that would need to be redesigned. They'd simply have to code the Z axis movement in.
Actually, that's where you're wrong. There are a LOT of invisible boundaries in the new maps which don't include the edge of the area, they're just ignored when you're on a flying mount. Certain rocky areas which look like you should be able to jump up onto, for example, have this. More obviously, many cliffs have this and not just the ones which don't have ground to land on.

There are several redesigns the old maps would need to work with flight. The major one being that some parts of the maps are clearly not actually modeled. I've noticed this myself in some areas of the Shroud if you get the camera angle just right. Imagine flying over a rise only to find the mountain is hollow and leads to a hole in the world. They do this to cut down on resources, since if you're not going to be able to see it then it doesn't need to be there.