Look up Spacecraft Manufacturing - they do exactly what you are thinking of, and turn 53 vans into some amazing RVs.
I'm a fulltime RV user with a 40' diesel, usually towing 20' behind me. But I also roadtrip in a VW sportwagen (also diesel of course!) and had a similar experience to the OP at the Pilot south of Tacoma. Not the little one close to the city, the actual travel center. IN A CAR, got told that I could only be there for 2 hours. WTF?
The Pacific Northwest has a major problem with people being homeless and apparently their answer is to just run off everyone equally, even those who are actively traveling and spending money. Fine by me, I won't return to that location with any vehicle of any size.