I once borrowed a home made cargo carrier that a friend built,he made it so it would tilt down and you could drive a motorcycle or tractor up on it without ramps..
I used it to haul my Yard-Man tractor around,I used to have to mow an uncles lawn in another town years ago,and soon found it to be a real chore to get it there and back--my pickup's stepside bed was too narrow to let the tractor fit on it with the deck on it,once I tried putting planks and plywood on top of the bed rails and drive the tractor up on top of the bed,that was VERY scary and top heavy,and loading and unloading it at my uncles house was difficult,as he only had one spot on the side of the street with enough of a ditch to back my truck into,and have the loading ramps more level..it was risky,cars would fly around a bad curve and my truck would stick out in the street a few feet..
The cargo carrier worked great,with one exception..with a 500 lb tractor hanging off the back of the truck,the rear springs would sag enough to let the cargo carrier sit only 6" off the ground,if that..
I had to be careful going up steep inclines,driveways,or store entrances with it,because it would dig into the asphalt and drag,a few times I almost got hung up,when it hit bottom,took the weight off the rear tires,and I had to stop due to an oncoming car--it refused to move again,my tires just smoked!..
I had to get out and lock my hubs and use 4wd to get the thing moving again!..a few heavy duty casters would solve that issue though..
But other than that,I felt it was a better way to transport a tractor than trying to drive it up into the bed..the truck didn't handle too well with so much tail weight though--I avoided using interstates with the tractor on the back,I stuck to the back roads..
I feared someone would rear end me too,with the distracted drivers around here tailgating all the time..