I think there should be illegal miners patrolling rich asteroid fields. The way I envision them is to have them be similar to hostile Ronin-class gunships guarding weapon stockpiles. The borers would be docked with asteroids and containers that contain mining related equipment. There will be hammerheads around circling around them. These would only spawn near places that have a rich ore deposit.
The context of such a situation could be that these miners discovered the rich ore deposit. They do not want to share the ore so they start setting up an operation. Eventually, these operations would turn into one of those hostile mining bases but at the moment, they are simply a group of miners illegally claiming the entire field to themselves. Mining stations could hire you to get rid of them and open the system to free mining.
The ships I would image holding these places would be Hammerheads II, Borer I & IIs. I would want higher level variations of them for later systems. There could be Hammerheads IIIs and Borer IIIs. The Hammerhead IIIs would probably use some Mayakev Moskva range of blast weapons, reactive armor, and Class II shields. The Borer IIIs would probably use Mining Particle Weapons, Heavy Reactive Armor, and Class III shields. I could also imagine seeing T31 transports docked with these cargo containers.