I've long thought it would be interesting to require players to attack through neutral territory to conquer an entire continent. This already happens when a "continent" is simply a set of diverse goals to hold for a bonus, but what if the continent was still a physical location, but with impassables dividing it into two or more pieces?
That line of thought brought me to the following setup:

This would want this to be just a part of a map. The entire "north wall" would be a bonus, but the outer "north wall" territs cannot attack the inner "north wall", or the central "north wall", without going through the corners first. I realize this would make the corners incredible bottlenecks, but I don't think this always has to be a bad thing. Holding the corners would be key to holding a wall, of course.
But my question is simply this: do you think such an element as what I drew above can be used in a map, or is something about its setup inherently bad for gameplay?