What counts as "too heavy" is very flexible. I have pulled about 100lbs behind me on a bike once without any problems, and you can certainly make this lighter than that. Hell, I've seen pictures of people towing refrigerators on bicycles. However, I doubt very much that any engineering cleverness will make this lighter than a tent + BOB trailer. What is the advantage that a camper trailer has over a tent?

If you do go ahead and build this, it might be worth it to make it possible to remove the camper from the trailer chassis so that you could also use it for general cargo purposes. If you have the money, you could look into Bikes at Work trailers for the chassis.

Another question I had concerns the disc brakes that are shown in your design. I've never seen brakes on a bike trailer before and I'd be interested to see how you control them.