I'm neither a martial arts expert, an operator nor do I find myself in regular altercations. As a fellow student (your very presence here grants you that position), I think I'd like to take a stab at this.
Some weapon is better than no weapon. Some training is better than no training. Mad Dog has a sign in his workout area which roughly translates to: "Remember, if you are not training, someone else is. When you meet that person on the field of battle, you will loose".
Well, based on that, Walt Marshall might someday be taken in a gunfight; Harry Humphries might go out in a Close Quarters Combat situation; Mike Mello in a HTH battle, etc.
The point is not that we become "expert"; just a bit better than we were last week or yesterday. If you look at it from that standpoint, your physical limitations are the constraint within which you will train, not a reason to avoid training.
When it comes to deadly force, especially the Edged Weapon, mental training is an extremely important first step. You need to really investigate your ability to plunge a blade into an opponent's soft spots; whether you're prepared to slash an extremity, and sense the tendons snap and let go like banjo strings. This is ugly stuff, but the alternative is often more ugly.
Once you've decided that you will, if required, defend yourself with whatever it takes, the single major cause of defeat is removed IMHO. The rest is all technique.
Look at the "tactical folder", for instance. If you carry a folder, it is incumbent that you practice deploying it while standing, sitting, moving or grappling. Whether you wish to learn to employ it in a reverse grip, for hooking and trapping etc, is completely up to you.
My point is that the trained fighter, who hesitates due to the need to ruminate the fight or flight decision, will probably loose to the man with a physical limitation, who is willing to do what it takes. Now, begin to add techniques (training) and your chances of surviving a trand and prepared opponent increases proportionately.