We use to have privatised police forces like the Pinkertons and they fought many battles against strikers, anyone willing stand in the way of the rich and they even performed false flag operations with impunity.
Academi (Blackwater) operates abroad in a very similar fashion to the way the Pinkertons used to operate, by performing military operations and sometimes they even randomly opening fire in the streets to incite the local population to take up arms against the US, so our troops have an enemy to fight.
It is probably not a good idea to bring this type of violence back to the US, by handing total control over the police to the rich, but like a train wreck, it would be interesting to see what would happen.
As far as Pinkertons and strikers go, there was violence on both sides. Strikers damaged plenty of property and continually trespassed on company property back in those days. Moreover, I can provide you with plenty of examples where private security did not do that. Case in point, the security company I worked for contracted with business and residential blocks. The only thing we called the police for was disposition of people who had violated property or persons, since in California, a private security agent can't take that person to the county jail.
Blackwater, insofar as they provide executive security, is an exemplar of high-end security services. However, you can't use their government contracts as some sort of example of possible behavior absent a state, since they are literally functionaries of the state.
I provided physical security and parking enforcement in one of the poorest neighborhoods in Orange County. It's not just for the rich, and if you allow for market competition, security services would be much better quality and much cheaper. Look at alarm companies. There's more than a dozen here in Montgomery county alone.
That's funny because "the rich" control politicians and city councils, and those people control government police agencies. What on Earth do you think we have now? LOL