I used to fly with a one legged pilot who applied full rudder trim in the direction of the missing leg and neutralised the rudder with the one leg he had. I tested a disabled pilot who had one leg much stronger than the other and recommended she try a similar technique.
I know a one legged flying instructor, and have conducted a PPL test on a paraplegic who had no feel from the chest down; he used a removable manual rudder control attached to the right hand seat rudder pedal.
British Aerospace Flying Club at Filton do a lot of work with disabled pilots, if you need any advice. Talk to their CFI.