Well put Rob.
As instructors, we need to also learn how get the fullest of of disabilities. If you need to teach a person that has only one arm, then you yourself, should use one arm for a bit to get the feel of how the students feels. That way, you know better how to explain something. Actuaaly I personally think every student should do things such as exercises, forms, and sparring with one arm, or one leg, or blind(folded), or deaf(ear plugs). To better understand that limits does not mean you have to quit.
There may be a time when you can use only one arm or leg, what if the lights are completely out or you're blinded by light. You need to know how to overcome these 'disablities'.
But that's just me.