Hoping it won't be seen as necro-posting, but I agree that armed civilian vessels don't really belong in the 2300AD setting.
For one thing, while piracy is possible (as it remains today), most illegal shipping activity will be contraband and smuggling illicit products, not hit and run attacks on ships. Modern pirates (like the Somali) either rely on ransom payments or on lawless areas where the sized ships' cargo can be sold and return to the world market somehow. In the 2300AD world, that would require, IMHO, something like a whole colony going rogue - and yet, being left to its own devices. Considering the level of social, financial and military investment required, I do not see such a colony ever being allowed to form and prosper, be that by the original colonial powers or by said colony's neighbors. Possibly one could have such colony operate temporarily but mostly as a front for another nation-state wanting to benefit from the sweet trade without directly commandeering corsairs through Lettres de Marque. Is it worth it though? Not so sure.
Mostly 2300AD is a universe of nation-states, which still claim to have a monopoly on organized violence like our current governments. France can be a hemispheric, space-faring nation, its power still comes from its ability to enforce French law and defend French interests, both things that are better done by French officials and French ships than by adopting some kind of "space Darwinism" to see if traders can compete with pirates.
One big evolution though, comes with the Trilon corporation, which has become both an economic and a geopolitical entity. As such, Trilon trading ships are probably a mix between a warship and a freighter (unless Trilon operates along a strict separation of trading ships and "sovereignty" ships).
