I rarely carry a fire arm the only times are man hunts and trans ports (sofar...) I dont like the Idea of it at all and I agree on the liability tid bit. Theres enough non-lethal options avaliable OC, CS, Bean bags, Batons, Tasers, dowel rods (fired from a 40mm or 37mm launcher), electric entry shields ect...
Further more, If you have time to set this rig up then this is already a pre planned use of force. Why have a single shot when you can use 7 less than lethal rounds in a 12ga? or 6 canisters of CS or OC? You train how you fight and fight how you train correct? So if you train in using your primary leathal asset in this manner whats gonna happen when you reach for this less than lethal device by accident?
My 2 cents. Im not a peace officer, I work in corrections so take it for what you