Starship: Cutlass Class Commercial Cruiser
Scaling downwards requires compromises, since some items are just fixed volumes.
Personally, I doubt that the iconic Broadsword is fit for stated purpose in Mongosian space (or Mongooseverse?).
I'm looking at purchase price of about a third of the Broadsword, with a quarter of the firepower and no smallcraft. In theory, you could patrol with the Cutlass, but you aren't likely to catch up with most commercial traffic, and a pirate is likely to be able to outgun you, probably outrun you as well.
Armament mix is divided between a laser and a missile battery, allowing the Cutlass to provide ground support.
If it acted as a straight out dropship, you could retain the spherical configuration, but I thought a neat twist would be to take a standard template, hollow it out and it really does become a commercial cruiser (and possibly a Q ship).
The hull could be built in any technological level ten shipyard, assuming you keep the armour; you could in fact half the armour.
And if you aren't chasing anything, or tagging along as convoy protection, you probably don't need a three parsec range range.
Using a commercial model allows more discretion and easier infiltration; making it streamlined, allows landing at covert locations.