During the Golden Age of Piracy (around 1650-1730), only two women are known to have been convicted of that ever-romanticized crime, and they were friends and comrades-in-arms. From what is known about them, Mary Read and Anne Bonny seem to have been in some ways opposites, a starting point I think could work quite well for a TV series. Also, some female-fronted pirate metal on the soundtrack would be terrific.
The facts about Bonny make her sound like the archetypical pirate badass. She stabbed a peer at age 13; she eloped with a small-time pirate to the Bahamas shortly thereafter; she ditched the small-timer for a swashbuckler of greater renown, Calico Jack Rackham; she proceeded to join his crew as a regular buccaneer in her own right, and never hid her gender. Johnny Depp justified Jack Sparrow's Keith Richards voice and mannerisms by describing pirates as the rock stars of their day, and if we extend this analogy you could call Bonny a Joan Jett-type figure. She loved robbing and plundering, so put another doubloon in the treasure chest, baby.
Read, on the other hand, had disguised herself as a male since childhood, and had lived a less jaunty life by the time she and Bonny crossed paths. She fought nobly in the British military and fell in love with a Flemish soldier and married him. He died prematurely, and Read (disguised as a man again) only became a pirate after her naval ship was captured by them. Bonny's flirting with her, which raised Rackham's ire, forced her to reveal her sex – and from that point on, their ship, the Revenge, had a dynamic female duo.
I could imagine a compelling “buddy pirate” dynamic between these two. Read, who may have been a good deal older, would teach Bonny about responsibility and taking life seriously; Bonny would teach Read about having fun and being comfortable with her gender identity. Although it's a bit of an obvious choice, I'd cast Janet McTeer, who was so good at portraying a 19th-century transman in Albert Nobbs, as Read, and Juno Temple, whose ebulliance and punk fashion sense would make sense for Bonny.