Whereas I cannot comment on the difficulties in using hand controls I can relate to the loss of a limb as I have a below the knee amputation of one leg. Motorcycle accident, another story. This was when I was 58 years old and an instrument rated private pilot. I was already active in our local EAA chapter and my first reaction (other than Ah S***!) was that this was not going to stop me from flying. My second reaction was to order a RV-9A kit. I remember assembling the tail and wings before I was even fitted with a prosthesis. Kinda hard hopping around with one leg and crutches and a rivet gun in one hand. After getting fitted with a prosthesis it took a few trials and tribulations to get the rudder / brakes figured out in a rental C172, but I did and the flight with a FAA examiner for the SODA (Statement Of Demonstrated Ability) was a non-event. Now I have no problems hopping into my (1/2 shared) C182 and going anywhere or, as recently, flying a bunch of Young Eagles kids. Life is good again (not that it ever wasn't) and I am absolutely confident that I will fly my, still in progress, RV-9A without a problem.
And, by the way, although I have not met him there is a gentleman at a nearby airport who lost both hands in a vehicle accident (Bonneville speed run as I am told) and he flys a Pitts.
We, as a species, are supremely adaptable and with the proper will power and attitude just about anything is possible.