I'm not generally in favour of occupational bans, but I think that's a great example for an occupation you should be able to get banned from if you are found to abuse your position of power (much like caretakers). You wouldn't want to see a rapist nurse be employed as a nurse or a molesting teacher work in a school, so why should police brutality be treated any different? You abuse a privileged position, you lose the privilege for a reasonable amount of time.