This is very interesting. I'd like a little clarifacation if I can. Basic construction is light wood framing with extruded foam. Covered in thin PVC foam correct? Why the PVC foam covering?
This is then covered in Polyurea. I take it this is pretty much the same thing as the spray on bed liners here in the US? Similar to Rhino Liner? Would a do it yourself product like herculiner or Water based tough coat work in a similar fashion. They are both tough but I haven't used either on foam of any sort.
Sorry if I sound dense. On another site there are many folks building small trailers out of extruded foam covered in canvas and woodglue / paint like an old airplane wing. Pretty cheap/strong construction. Looks like you are doing the same thing but with hi-tech covering materials. I'm really liking this design idea. Looks like it could easily be duplicated by a home builder. Just the concept not your exact layout of course.