Well here's an outside comment, but I fail to see how being seated in a wheelchair that requires using arms in order to move yourself through stations is an advantage when shooting. Arms fatigue, shoulders fatigue, hands fatigue, body fatigues - this is an advantage how? I am not familiar with any of the shooting sports so my question may be completely off target.
If I might be so bold but to suggest, if you would like to simulate the above conditions, try doing 10 push-ups in between each firing station.
I have no use of my left arm for anything and it is of no support or stability when at the range. I was also in a wheelchair and had to relearn to walk after lower body paralysis from a severely broken neck. I am also a Health and Fitness Edu. so I'm intimately familiar with A&P. An injury sustained as a result of nerve damage in the CNS is severely debilitating in regards to motor skill and muscular strength, not only in the immediate area but throughout the body. The body's anatomical structure for efficiency of movement and strength is based on symmetry, complimentary joints, and opposing muscle groups. When one part us affected, all parts are affected.
Granted, some equipment that is used for assistance may provide stability but assuming it makes any normal motor function easier isn't accurate. I know its cliche but I'll say it - unless you've walked a mile in those shoes, you can't fully appreciate just what it's like and how difficult it truly is.
I'll also ask, do the governing bodies who establish disability rules/allowances do so based on information and cooperation from any Physical Therapists inputs (or similar?)?