I completely understand on the desire/dream vs reality....it often sucks and that is the toughest lesson for a disabled person "to accept who they are now and the real life limitations".
I am the first to encourage someone to follow their passion...adapt, overcome & explore is the Disabled Explorers motto....but I would never tell a person to do something unsafe or unrealistic.
I have wanted a dual sport off and on for years...and each time I get myself ready to buy something (even the powered side car Ural) the reality of the fact that with my additional hip/pelvis problems I have 1 good fall left in me. Well I just move on to something else nutty 
I am glad to see you thinking carefully (something I often don't do!) and if you get a bike then it will be the best choice as you will have worked out the details. And if you don't it will be because you thought our the risk/benefits and you will be ok with it.
Either way I look forward to hanging out around a campfire together someday!
cigar smoking, wilderness first responding, ham talking night nurse who is overland certified and a fellow of the Royal Geographical Society.....
now everyone say "so what where have you been lately?"