The idea is, to have one choke point. Kind of a tunnel, which the aliens will have to take, in order to clash with you. So you cannot be outflanked. But when you place that extended workshop somewhere else (like ordinary workshops), the whole concept is undermined. I provoked this problem in my latest test game, where the workshop is pretty much on the other side. So I got two directions to defend, the one, where the main access lift and the actual hangar are placed, and the other direction with the enlarged workshop.