I agree with the sentiment above, if the goal here is to repair to make it look like it was designed, it's going to be very challenging if not impossible to do it without some salvage shell(s) or at least walls, plus a ton of work. But, if the goal is just to make the thing structurally sound and will keep the water out, even if it looks ugly and has little to zero resale value, then I bet with some creativity you could probably achieve that goal with copious amounts of epoxy and/or fiberglass as well as bits of wood and/or metal. You could, for example, simply cut out the damaged part of the wall on the front shell, put some new framing in for support, add some sheet metal to join that new frame with the old wall, and seal it up. I'm over simplifying, but that would be the general concept, with little regard for how the final product would look.
Dave