The best thing along these lines would be the hutts. I would love to see the hutts in there, but only if it didn't draw too many resources from the team's other plans.
The problem as I see it is that pirate factions in Legends lore aren't interested in capturing and controlling territory the way the warlords and other factions are - they are pirates, not would-be governments. I wasn't a fan of the Zann Consortium for the same reason; at most, criminal groups control a planet or two that they use as a home base (like the Invids), but these are never important planets with significant industry or populations.
Pirate groups are also never that powerful in terms of available fleets, certainly not enough to compete with proper navies - the Invids were one of the strongest we've seen and they had a grand total of one ISD2 and assorted smaller ships, while the Cavrilhu pirates later are stated to be a large band but to attack the Chimaera they couldn't muster more than a Kaloth "battlecruiser" a fifth the ISD's size and a handful of Corellian gunships and heavy fighters.
The only game I've felt really got pirate factions right was Distant Worlds - you fight, infiltrate, extort and hire your ships as mercenaries to make money. You build up criminal rings on planets owned by other proper empires, stealing much of their income, but your shipyards and bases are out in deep space and vulnerable if located. You CAN decide to start taking over planets you have built up operations on to a sufficient level, but once you do, you stop being treated like a pirate faction and now count among the empires. FoC's corruption mechanic was a step in this direction, but it was too simplistic and the ZC remained too focused on direct conquest and large-scale engagements.