No reason you couldn't, if you engineer it right. Watch out for stress risers where bolts go through the frame (like for axle mounts, etc.) But other than that, it's certainly doable.
However, if I were going to that much work, I'd be tempted to make a composite shell as well. Sort of like a Casita on steroids....or like that new one from Keystone...the Vantage. Sort of like a composite Airstream.
Cool thing about composites is they don't fatigue and they don't corrode. Man you could be the first to do it!
Best of luck,