There is no doubt that it will be a very small market. Most folks won't spend the extra money for the high quality product. That doesn't mean that there is NO market for a high quality aluminum trailer.
As far as "engineering" goes, I have to laugh at that. I've seen many factory engineered trailers that are absolute junk. If the holding tanks aren't falling out, the frame is cracking. What happened to the companies like Avion that built what the OP is talking about? They all went belly up because it was too expensive to do it right, and few people would pay the price. By the way, most of those old trailers are still out there waiting to be reconditioned.
If you look at some of the extreme rigs that come out of Australia, you realize that there probably is a market for a lightweight, rugged, trailer with good ground clearance and long suspension travel.
In my opinion, you will need a coil spring, trailing arm quality suspension that sets your rig apart from the others.
