Agreed properly regulating police (ie only allowing state police and federal ) and enforcing strict vetting would go a long way to solving some of the problems with the police in the USA.

The vast majority of cops are honest and do the right thing. Cops are human, it's unrealistic to think that Federal cops or State cops can be better than local by virtue of regulation. You cannot regulate away the flaws in human nature. The best you can do is detect them and deal with them when they cause problems. I've seen no evidence that the Feds or State police agencies are any better at this than city or county organizations are.

The one advantage they might have is different command structures. The state police are ultimately reporting to the governor, not a mayor so there might be fewer ways for a local political structure to use its police force improperly. But not sure that would really work in practice; it would likely just move the problem elsewhere.

Until the Ferguson outrage at least, a cop who did the wrong thing could expect to face, at maximum, a paid vacation as punishment. Maybe he would be "banished" to a nice cushy desk job upon his return to active duty.

Cops protect their own. Thin blue line and all that. But this sort of thing is what enabled sex scandals to run unchecked within the Catholic Church and if we let the constabulary get away with it, the public consequences could be far worse.

Having to pass proper vetting as in the UK would weed out some bad apples at the start and moving to \ single police body for a state would both improve the police and remove a lot of wasted tax payers money.