Police already have a less lethal device... it's called a Taser.
By the way, good luck taking down a "gentle giant" with a bullet in a pillow. You know, the guys that are trying to take your gun to kill you! Sorry, I want maximum lethality.
especially if he's a thug on PCP the size of Michael Brown. You fire something like that and he's just going to flip around and say, "can you rub the other side now"?