Welcome, Sadly I would have serious doubts that the frame is strong enough to handle any toys. Axle ratings there should be a metal tag on each axle giving mfg and weight rating. How are you going to reinforce the rear of the side walls if you remove the back wall? These things are built on purpose to have one wall support the other, and the roof holding everything together. Even if you were to safely reinforce the side walls and cut the back open for a loading ramp, anything you place back there is going to unload the pin, possibly to the point of making the whole thing unsafe to tow. You would be far better off returning it to a living RV and either tow it happy or sell it and buy a dedicated tow hauler.