Nice and clean.
However, I'd suggest you look at couple of things.
1- trailer basic weight. Its is heavy due to the axle, brakes and the 1/4" c-channel material used as the frame and tongue. It is heavy and designed to carry heavy weight across the frame.
2- height, due to the military requirements, trailer is designed to carry up to 1.5tons offroad behind a Hummer. The overall floor height is relatively high to clear obstacles offroad.
3- wheel/bolt pattern, due to military requirements, the wheel is a standard 8-lug 8 on 6.5 bolt pattern, same as those on the Hummer and late model heavy duty trucks. Tire size is tall to be compatible with the puller vehicle (Hummer).
4- foundation for the floor is rather wide and short which makes it difficult for a floor plan
5- coupling is a lunette
6- What is your estimate for a finished weight and what do you plan to pull it with?
You could look for a non-expanding shelter at the gov't liq auction. It weighs nearly 1000# and that would fit well with this frame and wheels.
If you replace the tires, wheels, and axle for something more kindly with todays trailers, you could save some weight. If you remove the tongue and restructure a lighter A-frame, again saving some weight. The frame is welded together so you will have some difficulty there loosing weight. You could remove the inner 3 crossmembers to help lighten that up and add lighter members where needed. The outer structure of the frame will be rigid enough for a camper.
I started off with something similar with a M101 trailer frame.
I swapped out the tongue and used a box tongue from a 2500# boat trailer.
Swapped in 14" tires, 3500# Dexter axle with parking brake (great feature for my driveway) but kept the stock suspension. Everything worked out well. I then added a slid in pickup camper from QuickSilver. It weighed nearly 1300#s empty. The slidein weighs under 500#s, so that makes the trailer frame 800#s+. That's heavy for a rolling frame.
