I suggest being able to jump out of the windows and perhaps use a ladder to climb back up to the top floor. It would really help open up the map. Otherwise, you could go deep into the back of the bottom section but if you wanted to get back to the top floor, you would have to walk quite a ways. Same thing for going to the bottom section from the top floor.
Of course, this is assuming that there will actualy be a full zone. I was hoping you would answer that question.