First we don't know if this unit has a single rear wheel chassis or a dual rear wheel one. Either way GM rated the chassis as a one ton chassis, just with a slightly lower load capacity.
The engine is capable of the load carrying as well as the towing, it just won't go up hills or pull away from a stoplight like a passenger car. The transmission and rear end might be the weaker links, but have certainly been used in more difficult environments successfully.
The real dilema with this situation for any smaller coach/chassis is the hitch rating and how much someone is willing to trust it. Where the dilema begins is the frame extensions added to the chassis by the coach builder. Under the best of circumstances it is subject to how well engineered it is and how good the welder was that day.
If I was serious about a unit like the one being looked at and I could connect an appropriate hitch to the original frame rails of the chassis I would not be deterred by anything else about the drivetrain assuming a supplemental brake system is used.
Opinions will vary on this, of course, but I base my opinion on a career in the welding industry and dealing with welding engineering on a daily basis.