Situational engineering

Coroplast 10 mil....Super Strong, Super light.  Cuts like butter, zip tie it or put bolts in it. Much lighter than plywood.   ...Flawed pictures, but designs should work.    

The Scion XB is a unique car with a lot of possibilities. The problem with sleeping in it, is all your stuff will  have to be moved to the front seat.     The other obvious problem is height.  If you are under 68 inches, you can build the false floor and floor bridge behind the seats and be fairly comfortable. If you are over this height , the answer to these issues may be to build a pop out box.    Build the box to fit through the back , and make a border around the gap in the hatchback doorway. Add a few folding legs for support.  Keep your things in the back of the box, and this will provide plenty of room.   Maybe even a kitchen set up in the back of the box, opening to the outside much like many teardrop campers do.    

The A frame is a portable shed and cabin solution for many. Coroplast is light enough and sturdy enough to provide some shelter from the elements, and privacy.  I see a possible portable cabin that is wheelchair accessible, for those confined to a wheelchair but looking for an opportunity to spend some time in the great outdoors.   The big plus for a wheelchair in this type of A frame would be no lip on the entryway floor, and having a solid floor.

The tent on the roof could be an A frame, or a pop up box.