as a former chief, i can tell you that you are living in fantasy land if you believe going into your city fathers and saying this engine, because of that canopy cab, must be replaced immediately due to safety reasons will have them telling you to replace it. The first thing they will want to know is does it work otherwise? Maybe even did it pass annual dot inspection and pump test. If it did they will be hard pressed to go along with your wishes to replace it. Heck, i am on an fd with a 20 year old front line engine that the fire board still refers to as the "new engine." the aldermen, or fireboards, or village or town trustees make the decisions on when they will release the money, hence they make the decisions on when those rigs are replaced. It really is that simple.
My bet is most rural fire boards or town boards would say don't let anyone ride in back then. Now what? Are you going to have 5 or 10 pov's cluttering up the scene? 2 guys on that first engine, now that should really increase fireground efficiency.
I rode on canopy cab apparatus for probably 25 of my 35 years in the fire service, split the other 10 years between tailboard and enclosed cabs. I never was involved in an incident where anyone was injured while riding in a jump seat under a canopy cab. Not once, and i never heard of anyone in my area ever being injured riding in a canopy cab equipped rig. The departments i was on had rules that said when running to calls, hot or not, you must be fully bunkered out, including helmet, one even required eye protection, and hearing protection was available. Obviously seat belts were mandatory.
Am i disagreeing with you that a custom cab pumper with a fully enclosed cab is safer than a canopy cab? Absolutely not. But the world isn't candy land and all the best wishes in the world will not make the canopy cab pumpers in service today go away for probably at least another 20 years or so.