Well there is a few options depending on how much arm movement you have, i am C4-5, so no tricep, wrist or hand function, just shoulders and weak biceps, you only need 3 buttons to control 1 stick and that's forward and left/right strafe, the other is controlled with the quadstick. So i lay a keyboard on my lap that has all the buttons pulled out bar 4 down the bottom, space cause it's big and you don't need to look at it or feel, and on the right i lay my hand on Num0 and Enter and you rock your hand between the two for strafing. Shift for ADS, but not needed.
I wish somehow people could see how i do this because writing it down just doesn't do it justice. In the last 3 COD's i have had a 3.0+ kd, top #100 in WoW raiding and multiple #1's in WoW DPS, top #10 Barb and Witch Doctor DPS in Diablo 3, and was #1 in Australia for paragon levels. i have completed over 35 steam games 100% most of which were FPS's and was top #25 in light levels for the past 3 destiny expansions. So with the extra 3 buttons that could be placed literally anywhere to have the same effect for eg; under elbows, back of your head (my mates a c4 with zero bicep movement and sits small jelly bean buttons under his elbows and uses shoulder shrugs and very few voice controls and he plays just as good as most able body people lol)
Trust me when i say you can still be competitive, there's just no other way to get this point across without sounding like some gloating douchebag so i apologise :(
I have spent the last 6yrs in a hospital bed doing this same thing everyday with similar but extremely inferior versions of the Quadstick and once i got my QS last year it's been like a dream come true.
Id stream but im too much of a pussy lol