I've thought a skid steer might be a good choice for the handicapped person. The reason for this is person is sitting inside. Some of the brands have joystick controls which means the adapting up isn't an issue.
I have a JCB 165 Robot skid steer. I like the side door. And I do believe it would be a snap to set up for transfers. There are as many if not more attachments available for skid steers too.
If you need a compact tractor I think I'd go for the hydro drive and I'd sure as heck try for shuttle shift.
I don't believe it would be too awkward to move the foot controls to hand operation. And a decent fabricator with a half a mind could bend up some pipe for hand use only access.
I think tractoring would be a great adventure for an amputee or even a paraplegic. A super quad I think would definately be better off in a skid steer.
Today as I was putting a gentle arc in a piece of steel using just a hammer and a table surface some thoughts drifted by. Sorta funny how that works. The hands get busy and they send the mind off to go bother someone else for awhile.
But there I was using a sixteenth of an inch high ridge and a hammer to put the middle of a half inch bar nineteen inches long just about a half inch high. Like I said, a real slow arc.
It never ceases to amaze me how that happens. There you are just hitting a piece of steel and the ridge is almost nil. Yet between the hammer blow and that ridge you can put the prettiest and smoothest arc in that piece that you've ever seen.
There's a real special feeling that sorta wraps you in it's arms when that kind of thing happens.
I find tractoring sometimes giving me the same high.
Now maybe I just naturally get higher quicker and easier than the average bear. But I doubt it. If I've done anything is I got caught in the flow one day and it's become an addiction.
If it's a thrill and a pleasure for a mental midget like myself then I'd guess it'd be fine for someone some folks call handicapped. I highly recommend you encourage that amputee to try tractoring. Of course you might have to go down to the store and get a grin bucket. They come in mighty handy when some of the grins are so special you want to show them off.
