I think Hyperion is onto something with his inherent limitation idea. If the culture of pirates impedes effective cooperation, they might end up being limited to small clans that can be defeated piecemeal. Norvell B. De Atkine, a retired US colonel, has written an essay about similar weaknesses in Arab armies:Talvieno wrote: ↑Sun Sep 10, 2017 8:28 pmThe issue here is that pirates don't actually have anything to limit them. They could conceivably figure out how to keep wrecking everything in sight until everything is gone - and they would essentially work like an expanding forest fire, leaving nothing in their wake but dead systems. Forever. As they went farther, they would gain more momentum, snowballing into an unstoppable force until everything in the center of the galaxy is dead, and continue to expand ad infinitum.Hyperion wrote: ↑Sun Sep 10, 2017 8:21 pmHowever, the stability of a faction that chooses to survive by piracy does have limitations, not explicit mechanical ones, but implicit logical ones. Pirates are akin to predators in a foodchain, they can only grow so much before "Steal this other person's stuff and/or kill them" stops being a viable option, and they either have to move to a new location, or start making their own stuff, at least the basics.
Why Arabs lose wars.
One may disagree or even consider this racist propaganda, but I think it describes a possible mechanism that could limit the ability of pirates to challenge other empires. Of course, it would require adding a sort of artificial stupidity to the AI .