Criminals who succeed long enough to have and maintain lots of military hardware are going to be businessmen about it. The unsuccessful criminal is not. This was as true in the 16th century as it was in the 17th, 18th, 19th, 20th, and 21st centuries. It will likely be so in any 31st century setting that doesn't have an express need to provide players with some easy warm up fights.
If BT needs easy warm-up fights, why does it have to be catch-all 'pirates'? Local outlaw bands on a planet would be easily as justifiable. So would a small mobilized dissident militia trying to enact change on a given planet. Or, maybe having to face down the retainer force for a Land Lord who has delusions of empire or has taken a grudge against a neighbor lord a little too far. Or, a small merc group who has gone afoul of the law (whether that accusation is true or not).
Think about the Dark Age right after the Blackout. You have the sudden rise of all kinds of rebel groups in the Republic. Eventually, many of them unite under a chosen House banner. But, before that point, they're not much better than 'pirates'. You didn't have to Leave a single prefecture for there to be lots of conflict, and that was the basis for the original MechWarrior Dark Age. Whatever you may think of the game mechanics of ClixTech, the setting had LOTS of potential, something
my group is trying to take advantage of while staging some games in that period in a unified campaign setting.
Plenty of start-up fights, for and against the standing power in the region or on the planet. Throw in hidden family Mech assets to treasure hunt for because of the exchange disarmament program, and you have something ready-made for a hero or four in short order.
And, it works
because of the black-out. No HPGs!
So, that's another question, and one tied to personalized BT choice. Do you have worlds
without HPGs in your setting? How numerous are they, especially in the Inner Sphere?
I know that there's not much support in fiction for those kinds of systems inside the Inner Sphere. Some are hinted at in sources whose canon standing on the subject is purely up to choice by design. (Interstellar Players)
But, there's room for them, because dots on the star map don't account for the actual amount of stars that should be on that map. I imagine systems like these would be something that sees steady traffic for some reason to justify their existence like special ore mining concerns. Others might be inconsequential, akin to small towns in the midwest US that largely have been forgotten but are still on the tax and election dockets. They're there. The government knows about them, and sends in surveillance to make sure that the system doesn't become a staging ground for an invasion force, but otherwise leave them alone, or maintains a flag there as a potential back-up place to retreat toward should things really go south.
(Look at the huge gap between Tharkad and almost every other system dot around it. That gap is over 30LY in many instances. There has to be some relay systems for commerce to the capitol system of the Lyran empire in there, because I can't see the Lyran economic juggernaut hamstringing itself with having to run a relay around to the one system which happens to be close enough.)