It's very doable. I've launched with our 35' Winnebago many times. Of course the larger the ramp the easier it is, getting yourself lined up is key. Walk the launch first and know your challenges. As other said you may end up with your tail end submerged, so scout things out and know what's back there. Our generator is at the tail so I can't submerge it, but so far in my 8 launches I haven't come close.
It really helps if you have 3 people, driver and two walkers that you can see going down the ramp but only one giving you directions. Rear view camera helps even more. Driver should stay in the motorhome, let the other two disconnect and launch the boat. Same goes for retrieving it.
As somebody mentioned finding somebody to launch & retrieve with a truck is a good idea. I watched an older guy with about 2 dozen cases of beer in his cargo bay do this. Said it was the cheapest way to launch/retrieve a boat since he didn't leave it in the lake over night.
Pic of our setup launching at Chief Timothy on the Snake River. Once we filled with water we lined up and launched easily, even with just my son and I. But this wasn't a steep ramp, for other steep ramps I'd never leave the motorhome cockpit.
