Gas motorhomes have the usual power brakes, and in my 30 years of motorhome driving I have never, to my recollection, felt I required excessive force to control the brake function. Adding a proportional braking system to the towed car, expecially a heavy van would be a must. I currently have the ReadyBrake, which actually pulls the towed vehicle brake peddle using a surge device. There are many options on the market. A minivan is a rather heavy vehicle, I am guessing over 5,000lbs, maybe by a lot. This greatly exceeds the Gross Vehicle Combined Weight capacity of many if not most Class A motorhomes. Be very careful in choosing a motorhome that can handle your anticipated towing needs. I am guessing that a Class C with a with an F450 or diesel or a Super C would be a way to go. (I am not an expert in this field at all, but there are plenty of well versed people on this website).
Can you do this: Why not. I've seen wheel chair modified motorhomes with lifts replacing the front recliner. If you can drive a van you can drive a motorhome.
Often the greatest barriers are the ones we create for ourselves.
Happy Trails
