Hi Webb Dawg,
Welcome to the forum.
That's going to be a tricky order, but not impossible.
I assume you would need a bumper pull instead of a fifth wheel, because the fifth wheels all have an upstairs and a downstairs.
Do you travel alone or with a companion? The ramps are all very heavy and the leverage to lift them is high off the ground (over my head standing up). Would you plan to use the ramp for your chair? If so, you'd definitely need to customize it somehow to get over the lip off from the ground to the ramp and then to get across the gap between the top edge of the ramp and the garage.
That video is pretty badass. Where was that?
I don't have any wisdom for you other than my 16 years of toy hauler ownership as an able bodied guy (unless clumsy is a disability). We have another forum here that have some good info. It's kind of a slow forum without tons of posts, but there might be something helpful there or at least people would be good about responding to any questions:
RVing with Disabilities and General Health IssuesI'd love to hear more about your boat-cart thing (land yacht?). How long have you been doing that?
I hope you find some help here. You're asking the right questions.