I am planning to build something like this for mine.
miniature horse trailer. Miniature horses in Arizona, miniature horses for sale, Mini horse cart, mini horse trailer, easy entry cart,
As it holds the axel of the cart, I feel it should be safe to use with the mostly wooden Meadowbrook cart, and bear the weight without really worrying about securing the wheels. My trailer has doors that swing sideways (rather than the ramp that must fold down). I plan to mount it to a single door, so in a panic situation, the door can still swing open, cart and all, to get the horse out. However, if I mount the cart so it sits a foot off the ground, the shafts would be sitting 13 feet in the air, and I have no idea what the minimum bridge clearance would be on roads we'd travel to shows or parades or whatever. So I'm still debating the logistics of it on a full-sized draft cart, but it's the best idea I've seen.
* Edit* According to TxDot, minimum bridge clearance is 14'6" so I'm clear in this state.
Those of you with experience, feel free to let me know any advise.