This has been a fun read so far, which is a refreshing change from the usual piracy / anti-piracy "debates".
Recently I was looking over the Deneb Sector book. In that it deals quite a bit with rival nobility engaging in various private wars. Mercs are often hired, huscarle fleets employed and letters of marque are handed out. Huscarle fleets have a size cap of 2000 dT for ships, so it keeps it a nice small ship environment more suitable to players (and deck plans and boarding actions with cutlasses, yaaaaargh!). Letter's of marque are only good against certain targets, if you have a letter of mark from Count Harold, that's good for attacking the huscarle fleet and privately owned trade ships of Baron Zarg or Baroness Volmesh but don't you even think about hitting that Ling Standard's freighter on its regular trade run, and if you attack anything belonging to the sub sector Duke, the Count never heard of you...
Long as you stick to the rules the Imperial Navy doesn't give much of a damn what you do, cross the line and you get zapped, period. Then there's that tense moment when an Imperial CruRon jumps in and you're wondering if the Baroness has managed to convince them you've crossed the line when you haven't... but really they're just passing through on a redeployment because you haven't heard the news yet that the Fifth Frontier war just heated up. So that's one possible campaign where players can play at piracy, mercs, and/or nobles with (small) fighting ships having at each other. I find the idea quite intriguing.
The other thing I'll note is that piracy depends in part on the economy and the economics of shipping. In the golden age of sail piracy allowed you to either seize a ship that was itself valuable or more often the cargo which was both valuable and portable, shipping was expensive and you didn't ship lumber half way around the world unless it was particularly rare and valuable. A modern superfreighter loaded with cargo containers of grain or consumer products will attract a different kind of piracy, there you're better off stealing either portables or else holding the ship and crew for ransom. In the latter case, if you aren't too greedy or violent and you're smart enough (*cough*) about it you might get away with it. The merchant line pays you a couple MCr, the ship and crew continue and its almost viewed as a "tax", that *might* work. Stealing some small launches and other portables, getting in and out quickly is probably more viable. Pirates always go for portable valuables, whether that's gold bars, spices, a small launch or a the crew itself. Being able to dispose of the whole ship and its cargo would be a plot on par with Ocean's Eleven.
As some have noted, public opinion will factor into it. Its not just simple economics. You can't boil it down saying "as long as they don't increase trade costs by more than 2% then there's no response but at 2.1% the Imperial Navy will be sent in." Its never that simple, never. The exact tipping point where the public or the trade companies have had enough and manage to get the Navy involved is one of those unknowables. You might think that hijacking a 200,000 dT superfreighter, murdering the crew and crashing it into a planet when you didn't get your ransom would be the tipping point... you might be right, you might not. People can be surprisingly oblivious at times and a few years later overreact to the smallest thing; so would be pirates take note and keep tabs on public opinion. Neither is invading another polity to wipe out pirates always an option. The Vargr are a constant source of raiders along the border, but I doubt very much the population of the Imperium would tolerate the Imperial Navy going on a mass campaign to smash the Vargr fleets. Sure, they have the firepower to do it and it wouldn't even remotely be a contest. But you'd have sophont rights groups going nuts and Emperor Strephon would be branded a racist in short order, and they don't impeach Emperors, they... well... we all know how THAT turns out (which ironically would make piracy a whole lot more viable!
) Or not, maybe you'd have anti-Vargr racism going mainstream instead, people can be strange... and the Vargr get blamed for the Emperor's death and it sparks a whole different war. Flip a coin if you like and have at it.
Then there's the points to be made about how long it takes to get news of what happened, response times, star systems are big places, and so forth. If a Frontier War can be fought and ended before the Emperor's response arrives, its entirely possible a certain pirate kingdom could spring up and strike terms before more than a Sector Duke could respond (and if a subsector or sector duke negotiating on behalf of the 3I "gave away the farm" so to speak, well... so much for their career).
Anyway, I think there are specific places and situations where piracy is viable even within the Imperium. But I also think they have to be taken on a case by case basis and some thought given to the who, the what and the why of each.
P. Sean ONeal
Writer / Artist / Building Contractor and space junky (or monkey)