The MH will have the power and the trailer brakes will stop the load "if" working properly.
As someone mentioned, the hitches and frame extensions are the weak link.
Since he is going to do it, have him take the MH to a good hitch shop and explain to them what he will be towing. They can put a 10k lb hitch on and if needed, add additional frame members to the MH.
I wanted to carry a motorcycle on the rear of a 32' MH and the shop wouldn't just add some pieces I wanted to the hitch w/o welding 6" C channel from the original framing along the extensions on the overhang.