I actually think it's simpler: create a special kind of tort citizens can bring against police departments for illegal policing (or other crimes against citizen

I actually think it's simpler: create a special kind of tort citizens can bring against police departments for illegal policing (or other crimes against citizens) which is funded (at least partially) out of the bonuses of the officers in question, and their supervising command staff, all the way up to the chief (regardless of direct command staff involvement, as an infraction against citizens is a sign of negligence); restructure officer pay by cutting it to 60% of the current value and giving them 50% back in bonuses, which can be phrased as a 10% raise; require that any officer which loses their entire bonus for the year through this mechanism be dismissed for being a liability and not be rehireable anywhere in the state. You'd probably also want to add in a law that created a special crime (or even just enhancement to suit damages) akin to evidence tampering for failing to create, lying in, losing, or damaging police records once a suit has been brought or is brought later and it's discovered those records were tampered with or negligently handled. (You could probably even tack in a requirement that police departments not hire officers which are fired from other precincts or who resign within X days of a scandal or as part of a settlement to that scandal.) Enough states have initiative laws that you could probably pass it based on popular sentiment. In the state I'm from (WA), the legislature requires 2/3rds vote to change an initiative within the first 2 years. This provides enough political cover for inclined state legislators to support it, as all they have to do is do nothing because "the will of the voters". It's also politically dangerous to overturn an initiative within those two years, because it's going to be phrased by the press as suppressing the "will of the people" or what have you. This structure is actually how many of us are paid (a base rate, a bonus for a good job, and being fired if we can't do the job right) and only requires that the majority of voters think we should hold police accountable for crimes. I don't think all police officers are trying to be bad people, but I do think that the system is set up where they're basically forced to join in conspiracies to commit and cover-up crimes against citizens. There are, however, lots of little ways we can change the system to make it more reasonable and punish bad actors.