While this is definitely needed, I don't think it's a starting point.
IMO, a good place to start is instituting policies requiring LEOs/PDs carry liability insurance. Similar to doctors and other medical practices (in the US). An officer is found guilty or misconduct or violating a citizen's right? Penalties are taken out of their insurance and their premium increases. Can't afford the premium? Guess who's looking for a new job?
The way I see, the pigs can keep their criminal immunity, but civil matters will have a more direct financial incentive for them to behave like they have morals.
So we'll march day and night
By the big cooling tower.
They have the plant,
But we have the power.