I think it would be very difficult to try to crimp an LP inflator hose quickly. It's a different story with a regulator hose.
Hose hats help, but if the fitting is stiff enough, they WILL pull back. I have learned to periodically put my LP inflator hose fittings through the ultrasonic cleaner and then use some silicon spray on them. It helps enormously.
A DiveAlert type horn is something you use on the surface, when you get there and the boat isn't near, or you need to get someone's attention. It seems to me that it should never be an emergency thing; you should always have time to get it out of a pocket. To establish buoyancy, you can orally inflate or drop weights. I suppose if you were dodging a shark, you might be in a lethal hurry . . . but short of that, you have time to deploy a marker buoy or get out your horn. On the other hand, a stuck inflator is a potentially injurious or lethal problem. I wouldn't insist on keeping a horn installed, if it interferes with coping with a much more dangerous problem.