I advocate for them having a 'makeshift capital ship' at maximum threat level. Like salvaging an obsolete asteroid-cracker miner ship and tweaking it for offensive capabilities. Being a miner ship, it is a tanker hull by design, as it must both carry heavy loads and resist unintentional impacts, being an obsolete piece of junk which has no shields.
Tractor beam: disables ship engines, prevents ships from jumping/turning.
Mining laser: high-powered laser used to atomize rocks retooled to atomize hulls.
Berzerk!: pirates take (highly toxic and addictive) chemical stimulants to fight better, faster, and put weapons on overdrive (lower weapon cooldown, higher damage, faster turning and ship speed)
Boarding parties: Avast me hearties! Only effective against corvettes/frigates/cruisers. % chance of taking over ship.
That IMO fits completely with pirate lore, and would be a nice adition.
I also think that the Pirates should have difficulty levels. It couls be a simple 3-level, or go along with the empire AI difficulty, going all the way to cruel.