As I befriend Pirates, and going Palpatine on the Pathers, giving Pirates a leg up in ship tech would give Pirate Armadas more teeth to use in raids against other factions. If you focus on befriending pirates by doing exploration missions for them, pirate fleets will leave you and your faction fleets alone and not even raid your colony even if your colony is targeted with pirate activity.
On the funny part, the pirate raids on Hegemony systems give patrols plenty of distraction for my stealth fleet composed only of Valkyrie transports with insulated engines and augmented drives to do some clandestine chaos of my own without causing hostilities. The best possible chance I can do for finding faction blueprints, especially the coveted Battlegroup XIV ship blueprints.
As for you selling Hyperion blueprints to pirates, I'd say let them fly ballin' in those ships. They have key weaknesses to exploit.