That has been my thought all along for the past couple of years. My folks did that with two vans. The first one back in the 70's when van conversions weren't really around then. But my dad found a place that built a dinette system on a plywood floor that converted into a full queen bed when you wanted it llike todays camper dinettes). The benches were hinged on the botton and could be folded in so that if you wanted to you could pull the whole thing out and use the van for something else. Mom made curtains for it and we just took out the back seat when they were going to camp or whatever. Later on this unit was transferred to another van and they camped all the way out West to CA and up into the Canadian Rockies and back for a month with it. Just put food in the cooler, took a Coleman stove along and their personal stuff and HAD A BALL. Stayed out a couple of nights in Yellowstone at a log cabin cause temps were a bit too chilly to sleep in van, but that was it. Oh yeah, had a vent put in the roof and a plug into the one side to hook up to electric. The only issue tht stops me from doing this right now is that I don't like driving those vans on slippery winter roads here. One thing I have been looking at too is Sportsmobile. They will convert vans to anything you want even if its just a bed back there. Look up their website
www.Sportsmobile.com. Anybody had any experience with them?