Craig, there are bass boat trailers with folding upper boat cradle, as you describe. The upper rack folds down, run the boat up onto the rack, and it powers up like a car hauler. Then you load the lower boat and you're on the road. I would guess that these trailers are right expensive.
Regarding low profile golf carts, an old gas powered Yamaha is what Bill ...aka "Homegrowndie".. has stuffed in his Eagle bay. It would fit into an MC9 too...with small wheels...as has been described already. His steering has a universal in the steering shaft so it'll drop down. He cut the column and added a sleeve to the outside. Believe the sleeve slides upward and the shaft drops. When the sleeve is slid downward, it connects the upper and lower sections of the column and the steering is in a normal position. This is a fairly accurate description of what he did.
A belly golf car is going to be "personality limited." No lift kit, no 12" wheels and tires, no top, no big plush seat...
...could do the 72V mod..
That'll mess with the campground owners. Might as well forget the custom paint job too...get all scratched off trying to get the car into the bay.
Another thing I've run into with my stock height Club Car is that the sucker will bottom out on my trailer. Usually we can find a low spot to unload it...a PITA when towing with the bus. Redoing the ramp is one of those things that keeps getting put off....
In any event most motorcycle stores, and probably Northern Tool and Tractor Supply sell arched aluminum ramps that have a capacity of 1500 lbs. These would allow one to roll right into a bay with the car almost level. They would store under the cart.
Something else I've run into is that ATVs, UTVs, gasoline powered golf carts, go carts, scooters, and other gas powered toys are not welcome in most bonafide campgrounds. Ya'll know where you're going and the requirements...this is for those with little experience in campgrounds that may be thinking about buying gas powered toys. I'd be riding a Yamaha Rhino or Kawasaki Teryx ( the ultimate off-road Man Toys when properly assorized) if not for that requirement.
One other point and I'll be quiet for a bit (yes, I promise), quite a few campgrounds will require proof of liability insurance before you unload the cart.
Recommend tongue weight is 10% ...could be tough on some bus cantilevers. Most light trucks and cars with this much tongue weight use weight distributing hitches. I don't see how that would work on a bus....
If placing a golf cart 5' above the deck of a trailer, that better be a heavy duty trailer...on the order of an equipment hauler I would think.
Well, we've gone full circle here...still appears that loading into a pickup toad is the cheapest, most safe, and easy on the bus.