I think you are looking more for the concealed type wheel lifts like the repo guys mount underneath the bed of a standard pickup truck for stealth. My buddy bought one of those used a few years back and put it under his F350 dually with cap. Once it was on you couldn't really tell unless you were looking for the extra hardware hanging under the back. Slick set up. When retracted you don't see it. I would think something like that would just as easily mount under a motor home frame with a little fab work. You would wand to do some careful head scratching ahead of time to make sure it doesn't need to occupy the same space as something critical that is already there like a water tank. Also, I would want to check the specs on towing capacity and particularly tongue weight for the motorhome, you tongue weight is going to basically be the weight of the lift unit PLUS half of a car. No problem on a truck conversion, but most standard motorhome chassis don't have a lot of towing capacity. I know of 2 different guys in my business that literally broke the motorhome frame in half (one was a big pusher, one was a class c) towing too heavy of a trailer.
As to towing a trailer with the stinger, it is done all the time. I have been rescued with my dually on the rollback and trailer on the stinger. I used to have another buddy in the wrecker business, sold his dually and just used his medium wrecker to tow his 48' gooseneck with the stinger when he needed to. Admittedly not long distances, but still.