This sounds like a good idea on paper, but the administration costs of that project would be astronomical, or if its run by volunteers, then data integrity comes into question.
I like the idea of using the insurance system instead. Treat cops like doctors and force them to carry a form of malpractice insurance. If you fuck up, then the bill isnt paid by taxpayers, but by insurance instead, and then your rates go up and eventually you become too expensive to hire. Additionally, it also gives police departments an incentive to hire cops that are less likely to treat the public as a threat to keep insurance costs down.