The spray foam is a nice idea for structure, but it's much better if you put the structure together first and then press it into a mold and then inject foam into the voids from the ends. They do similar for structural panels for houses (called SIP panels, we've long considered building a house from them).
I also concur on the innovation angle. For the price, I'd grab a Okanagan 126TKS (I think Eagle Cap makes a follow on version, or did), which has the same interior space, does not require a flat bed truck. Both still require a 550/5500, but I rather like the idea of having a regular truck bed when the TC is not on.
Jim
