Bachfish bought a former Naval Auxiliary Transport (armed)-now Pirate's Bane"- from the Andermani and bought another one. The Andermai were very aware of who they were selling the ship too since they sold it with the weapons capabilities intact.
This was a former RMN Captain with a very good record of anti-piracy patrolling in Silesia who ran into political problems which caused him to be beached so he opted for one of the traditional options of a RMN sailor and went into the merchant services as an owner-captain. Of course he then had help from ONI but the cover story is the best kind- it sticks to the actual facts of what happened, just doesn't mention that he is getting supported and paid by ONI. He most likely has silent partners who provided some of the acquisition and startup costs as an investment (nice way to hid ONI involvement, you can send the profits to a shell corporation which is a good way to screen that you are the sole owner)
He is working Silesia, which is a place he knows well from his service there. He also knows and understands the problems (all the problems from the local politics, the piracy, the indiffernt capabilites of the average ConFed Navy commerce protection, probably the interdependence of various politicians/merchants/pirates). So, when he takes his pension and savings, he buys a surplus naval auxiliary which can be rearmed (or buys one with older weapons systems) and upgrades them.
The Andermani understand the need to provide your own security in Silesian space and here is a former Navy Captain who has a track record of being able to do that. He's being open about what he is doing. Heck, naming the ship Pirate's Bane is both a warning and a not too subtle hint that the commander isn't going to let your garden variety Silesian pirate survive an incounter. So he gathers a crew of people who can take up to Naval level discipline, run a for-profit shipping operation and has them trained a RMN level of competency to fight what is probably armed to some DD level of weaponry if somewhat older equipment. He gets the licensing he need to run an armed freighter in Silesian (and Alderman) space. He does well enough that he and his investors have bought a 2nd armed freighter to expand the business.
Bachfish is hiding in plain sight. He isn't doing commerce protection patrols, he is his own protection as he works the cluster in commercial traffic and shipping. That he collects the bounty and prize money from capturing or destroying any pirate craft that ATTACK HIM is just gravy as far as the Aldermani as well as the other ligitimate merchants in the area are concerned. He obviously gets satisfaction out of destroying pirates, he just no longer goes looking for them, they have to make the mistake of comming to him while he is now making a living hauling cargo and brokering shipping deals though the cluster.
The Haven operation sees a successful merchant who isn't doing anything odd. Bachfish is applying his naval experience and passing on information to ONI but he is also going to make field judgements about things that need to be followed up. That brings him into the fight with the Haven DD but it was a calculated risk that he might have to fight because there were too many odd things with the Haven operations pattern.