Just a couple more brainstorm ideas. I think if it was me, I'd like to be able to manoever around in the raised position, and not have to lower down to change position. One could always grab hold of the lathe bed, or the stand and push yourself around, but eqally important might be to be fixed in position, so you have something to leverage against while operating the machine. Castors with brakes, with extended rods for control of them? Also, is this wheelchair electric? Is it possible to attach four electric 'jacks' ,which become legs when extended- no rolling around this way- maybe rotated through a single motor using bicycle chain and sprockets. Whatever mechanism, it may need to be 'chip proof'. No good if it can get jammed. Something like that could be used anywhere an extra height is needed. Of course, it adds weight to the chair.
I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-