I store my airstream and Volvo at an old Nike Base (missile - not shoe), and in one of the underground bays are a couple of welders who make Kiosks for cash machines. They have for storage - containers that came off ships. Now these containers are all steel, built like a brick out house, are 102 inches wide, at least 8 ft tall, and 20 to 40 feet in length.
You can buy these for about $2500. There are so many of them in this country as we import a whole lot more than we export. Now think of what an ugly but strong enclosed car hauler they would make. Would need a big truck to pull, but hey we have big trucks. These have only been used once and are like new. Gotta be a use for them some place besides storage.
Frame rails, and a couple of axels and good to go.
May build one, just to have the uglist trailer on the planet.