First I am so sorry that the disability keeps you from what you love.
I can only speculate but what about wheel chair that is raised up to the elevation to a comfortable point to work from. The only thing I would be worried about is the center of gravity. If you look at the wheel chairs that the basket ball players use to play ball with the wheels slanted outward to help displace the balance problem. If it were a bench top shop that would be easy just drop the benches, but with big boy toys we need to have the height and to get there is the problem. I wish you all the best and I feel with a little imagination you can over come. You are a machinist are you not?
Good Luck
Nelson