That's what Tom's talking about with the running gear, but it wouldn't need to be that stout. Hay wagon's meant for hauling multiple tons of hay. A blind really only needs to be built with a reasonable safety margin, and typical construction would meet that easily.
There's a lot of mobile blind trailers out there, but all of the ones I've seen are over complicated and made more for rolling down the interstate. I'd be more inclined to build something on some skids and move it when the ground is frozen or add some wheels to roll year round, then keep it from tipping with guy lines.