I think you're on the right track for your wants and needs....
Power Trac used to offer a 3pt hitch on the rear of some of their models. They did away with it. Why do you think they did away with it? Why do I think they did away with it?
I think they did away with it because:
A. Nobody was buying it.
B. Since they only had one speed range, they had to compromise, so they didn't have enough grunt for ground engaging implements like dirt plows.
C. For the very few times that most of us PT owners would like to drag something along behind us, we can drive backwards and not be too upset, given the benefits of everything out front out-weighs the drawbacks of the occasional look over the shoulder.
Take my firewood gathering, for example.... I drive into the woods forward at 8mph, grab a tree with the tongs on the FEL arms, and I back out at 8mph dragging the tree along looking over my shoulder. If the FEL arms were on the rear, I'd have to do a little turnaround dance at the log, then try and back up and grab the log while looking over my shoulder. I'd rather hook up forward and skid out backward.
So I take your driveway grading example, as that's a very good example of a drag application...
The PT425 has a rear pin hitch. So why not just use something like a DR Power Grader and drag it along with the PT?