It would make more sense to have a licensing body or multiple that are all connected, use the same processes and can strip a license.
Doctors, nurses, lawyers, teachers all over the US already have licensing requirements, ongoing training requirements etc.
Edit to add: I live in Minnesota and Philando Castile was shot and killed by a Saint Anthony police officer in Falcon Heights. Falcon Heights used neighboring Saint Anthony’s department for their city as well. Outsourcing to another agency/department doesn’t address root cause of policing issues.