This is very interesting, Grace. I never really thought of Fletcher Christian and company as pirates in the usual, plundering sense, but I guess they were in reality, given their illegal act. As well, very much like your analogy of pirates as outlaws on ships instead of horseback.
The idea of a possible genealogical bond between Anne Bonney and Billy the Kid ("BTK") is intriguing, but doubtful, as the name, "William H. Bonney," was an alias. He was born William Henry McCarty in New York, and his biological father is unknown. Historians are also not sure if McCarty was his mother's maiden or married name. After a time, she married a man named "Antrim," and BTK was known as Henry Antrim and even Kid Antrim. As well, no one can pinpoint for sure where the surname, Bonney, came from or when he started using it, and speculation runs wild with all sorts of theories. So, fiction would lend more conjecture to the mix and possibly be no less plausible than most of the little-known history. Hope the bunny inspires you to move forward; it would make for interesting reading.