Very creative. Gave me some new ideas that I never thought of. Start with making some sort of support for the corners so it doesn't shake when moving around while inside, or flip back if too much weight behind the wheels. Are you leaving it hooked onto your hitch while hunting or will it be disconnected to park somewhere else?
If you cut a removable hatch in the floor, it can double as a ice fishing hut.
For the corner supports, either use 4 car jacks or some steel pipe with an over sized flat bottom and multiple holes drilled through it so it can be raised and lowered by bolting them on or a pin system. The cheapest pipe system would to buy some black pipe and floor flange at home depots plumbing department.
A big difference in design is if you have a welder or not.