If I was in charge of replacing the police, part of the changes would be limits on serving as an officer and other roles. This would encourage fresh blood to replace the old, and help prevent corruption: Former police officers can end up under the batons of their successors, if they don't ingrain good values into the next generation.

By breaking up the career and authority of police officers into discrete chunks, we can also prevent power accumulation via social bonds among them. Something like:

1 year of academy -> 3 years as officer -> 1 year paid remedial education -> 3 years as officer -> 1 year paid remedial -> 3 years as officer, etc.

While we would lose raw efficiency due to elections, education requirements, and so forth, I think something like this would help prevent police from becoming a vile cornerstone of society.