Speaking as the guy who designed the stats, the Picaroon is a light dogfighter derived from the general idea of the Sai but based directly on the Corsair's design. That didn't turn up in the fluff but the art and the model number both point back to the older fighter. The armor level isn't a coincidence, either, nor is the fact that "picaroon" is a synonym for "corsair". I didn't write the fluff but did get to add some to the art notes, so the official writeup doesn't reflect what I really had in mind.
So what's a bird based on a Davion signature fighter doing in the former FWL? House Marik used to have a Corsair production line on Connaught that was destroyed very early in the First Succession War, with most of the survivors winding up with the Regulans over time. When the Regulan Fiefs wanted to build their own birds, they looked at these old highly survivable Corsairs they'd been flying for centuries, knew inside and out (they've probably built aftermarket kits to maintain them for that matter!), and used them as a starting point.
EDIT: Thinking about it, the F-95 Stingray was probably on the Regulans' mind as an upgrade. They were using the CSR-V12M Corsair variant for a long time, which has just the one large laser, so the F-95 is a logical place for them to look at for ideas on a "single big gun" fighter.
