I seem to remember that in the early days of 747 ops something similar was available for the all pax aircraft.
Basically a smaller scale unit which occupied a door-side position on the lower deck. You would use a forklift to get it out and what you had was an elevator to bring the ULDs down to ground level and vice versa.
Remember back in the day a lot of airports did not have ULD handling capability as most of the planes were narrowbodies.
Anil