Having had several camper vans and RVs and taken them all places I probably should not have, I'll never have another RV offroad. Not a mass market RV I mean. I paid particular attention to one thing you said, washboard. For this reason alone, plus your towing plans, I would strongly consider a truck based camper with a small/closable pass through. I'm meaning pickup chassis cab with something on the back. The constant rattles from every van I've had and most certainly my lifted RVs were enough to split up a family. Just constantly unnerving and frustrating. They are all this way, except perhaps an Earth Roamer/Cruiser type rig.
If you have the means to build or acquire this you'll get OEM 4wd durability and more towing capacity than anything else, plus you can close the door to the noises coming from the back while going down the road. You'd like to think that Sportsmobile and some of the other marketed offroad type vans/RVs were immune to this but not in my experience. If you are within earshot of anything built of wood containing all of your gear it's going to rattle, shift, etc.
I fondly remember one particular night trying to get to a campsite after dark near the Tetons. We knew the place but recent rains had made the road muddy and rutted. I had a 2wd dual rear wheel Class B plus thing (Itasca Cambria). My wife spent the last 30 minutes of a very long day running around the back holding cabinet doors and drawers shut, picking up their contents, screaming at me for simply trying to navigate the road, getting seasick and generally cursing my existence. Good times.