If you can drive a E-350 Ford van with those power brakes and gas controls, the E-350/450 minimotorhome and F-53 motorhome (class A) use the same power steering, and other controls.
I think one of the modifications is to raise the power steering pressure, so it turns with less feedback, but is really easy to turn, and might even lessen the power braking effort required.
Before making the final decision on a RV, you might want to get the controls company involved that installed the hand controls on your minivan. They might say that any E-450 based motorhome will use the same controls as the E-150 and E-350 full sized vans, straight off the shelf parts. Those some controls might fit on a class A and might not. It depends. My motorhome is a 97F-53 chassis, same as the Ford van steering wheel of that model year, same chassis as the F-450 truck of that model year.
Raising the power steering pressure should be the same as the F-350 van. They do this so you can steer with one hand, and use the other hand on the brake / gas lever. (some reading this might not have driven a handcontrolled van).
Try looking on
RvSearch.com for a RV with handicap access. Sometimes I see them.
I have also been typing in Handicap to the "For Sale"section of my local Craigslist.com and sometimes a motorhome will show up.
Check with Roadmasterinc.com for possible baseplates for your minivan. If the van based motorhome is short enough, it might mean taking along the minivan is redundant.
Good luck!
Fred.
