...that is an excellent idea
...that is a terrible idea
...hmmmmmmm, food for thought Ron.
...schedule 40 PVC has excellent crush resistance but has very poor resistance to flexing, which is what you would want in the wall of your TD. Once everything was built it may do OK but you might have real problems with warpage in your walls before they are installed. You would probably have to go with 1.5" or 2" to have a hope of avoiding flex problems...furniture made of PVC is usually made of 1.5" or larger sch 40 and is cut into short pieces so as to combat those types of problems.
Another problem would be the tendency of PVC to shatter at lower temperatures(approaching freezing)...in the plumbing industry when temps go below 50F it is recommended that you preheat PVC before gluing
The idea, on the surface, sounds like a good one but in practical application I would have severe reservations about using PVC as a structural component ...the little trailer in the pic is a lawnmower trailer and in that application would probably work fine as long as temperature stays high and it is protected from the UVies
...all this is IMHO and as always YMMV
madjack

...I have come to believe that, conflict resolution, through violence, is never acceptable.....................mj