That is one excellent trailer.
There were some truly amazing Safari trailers at the LandRover World Show, every mod con. Price around £10,000.
They had a kitchen with cooking facilities, fuel & water storage, roof tent on top, cooking utensiles, plates(China), glasses etc all with custom made holders to stop things jiggling around and breaking
I want one but can't aford it. Its 4 times more than I paid for either Land Rover
Seeing the trailer in the post though has put me in mind to build something similar, coil sprung would be good