On my friends B7100 a plumbing nipple was welded onto the
HST rocker foot control peddle.
He screws in a short length of 1/2" pipe and runs his BX by hand with that.
Push lever for forward and pull for reverse.
Center is neutral/stop.
Works real good for him.
While he has good walking ability, a damaged tendon prevented him from operating the foot control, so he does it all by hand.
A good KISS solution! (and 10 min conversion!)
Additionally a 'dead mans switch' (as used on snowmobiles and jet boats) could be fairly easily incorporated to activate the fuel shut off, 'just in case' as an additional precaution.