Much as I like & agree with the points you've made here, I'm not certain I'm entirely satisfied. Because when all is said & done, doesn't it still leave the public at the mercy of "in policy"?
E.g. go back twenty years, when LAPD Officer Tarriel Hopper shot actor Anthony Dwain Lee to death at a Halloween party on LA's Westside. Summoned to investigate a noise complaint, Hopper thought it a great idea to wander around, instead of waiting for security to bring the hosts to him, where pretty much everyone would assume he was in costume, too. He spots Lee in a backhouse with other guests, shines his flashlight through the window, Lee spins around pointing a prop gun his way, & Hopper responds with a deadly fusilade.
Two days later then Chief Parks tells the media that Lee left Hopper "no choice" i.e. the killing will be found in policy. No question of why Hopper put himself & everyone else at risk wandering around solo in such a circumstance.
Fast foward: Scottsdale, AZ. A call from neighbors that John Loxas threatened them with a gun. PD responds with sniper extraordinaire James "Shoot 'Em Dead!" Peters. Loxas comes to the door holding infant grandchild & cellphone. Sees police. Turns aways, Peters shoots him dead from about twenty feet away. PD finds it in policy (but finally decides to retire Peters, figuring six kills is enough for any cop). Officially, however, their hands were clean.
In short, there's really nothing to critique the brass for when shit like this is found in policy.
Granted, you don't claim to solve ALL law enforcement issues, & I think what you do propose is worthwhile & long overdue. Returning liability might be the single most important step we can take to facilitate police reform.