I think applying to cops something along the lines of what we have for professional engineers, doctors, lawyers, etc. could be a solution.

All cops nationally would be required to have a license from this organization in order to do some "reserved acts", like arresting someone, using force, firing a taser, etc. Any complaint about cops would be evaluated by this organization, and could result in the suspension / revocation of their license. There would be a strong emphasis on deontology, and the organization's explicit mission would be to protect the public.

This would probably have a similar effect overall to what you're describing, but it'd be more of a whitelist than a blacklist.