I'm sure it could be done but Apple need to solve it. To get to use my iphone or ipad I'd have to get my carer to set up the holding stand, pass me my mouthstick, set up the phone or pad to my head, login to the mac, pack away my mouthstick and iphone/stand, once logged in I can use touch id but the distance I have MBP away from me is further than my arm will reach so carer has to move laptop, pickup my arm, use touch id which doesn't work so well with someone else moving your hand then get my laptop positioned again. It is far simpler just to give my carer the password.
I could auto login thus not having the carer know password but which is the least secure?
There should be the ability to launch a keyboard at startup.