Requiring the police to live in or around the precinct they work in, regular surveys from local residents about their professionalism. Increase oversight on funding (no more margarita machine, bitches), ban the use of military grade weapons and vehicles by local police departments, actually prosecute in accordance with the laws any cops found violating them, ban re-entry into the force after you are found committing a felony.
There are a million things that can be done within the current system, but they just don’t want to because cops, DA and judges are a huge racket.