My old van, and probably the new one when I get it, used a bunk crosswise behind the seats. 24 inches wide, 3/4 inch plywood resting on 2x4 brackets bolted into e-track load locks. It had a custom made foam sleeper, slept like a log. I usually left it up and could sleep there on all-night runs for naps, also during times when I had a load that I had to keep over a weekend or overnight at the receiver. If I needed extra room, the mattress sat on edge behind the seats, plywood up next to it, wood brackets came out of the e-track and got stuck somewhere, such as the step-well at the side loading doors. Only took a minute to set-up or tear down the bunk system. Then I had lots of load room for longer loads, and if I knew I would have to sleep with a longer load, I got a motel. But I made sure the company paid toward the motel, or that I earned enough extra on the load to cover it. Probably only one load in 20 that I needed the last two feet of cargo space, and very few of those required holding the load over night or over a weekend.
One modification I will make. The brackets were only about 2 feet wide and I had one in each e-track, so one on each side of the vanwith the plywood board extending across the van from one bracket to the other. Next time I'll make them so that each sit crosswise in the van, with one end in the passenger side e-track, and the other end in the driver side e-track. That way I can move them as far apart as I want, put the plywood on lenthwise instead of crosswise, and sleep lengthwise when space permits so I can really stretch out, and so the brackets can also be used as moveable and elevated load bars, which will be handy for barrels and other odd-shaped freight. I had a small wire three shelf stand that fit nicely
next to the wheel wells (got it at Crate and Barrel, or similar place)
and stored my non-perishable food and plasticware on it. Bungie-cords, of course. Golf bag bungied to the opposite wall near wheel-wells. I didn't worry about keeping food cold....with a van, you can just pull into the grocery store and buy cold stuff whenever you need it.