This is my suggestion on what pirate ranks could be like and how they could function.
Since it openly states on the pirate page that pirates have no rulers I will not add as many pirate ranks as nation ones.
1.Powder Monkey-equivalent to a citizen of a nation. No benefits aside from not having to pay ship taxes, 5% bonus in fame gain and halved upkeep.
2.Gunner-Equivalent to a captain.-Same benefits of powder monkey, plus 5% more bonus in fame gain, recruitment and cannons are purchased half off.
3. Quartermaster-equivalent to a major. Same benefits of previous ones, plus skirmish costs half the turns, and escape chance is halved.
4.First mate-equal to Colonel- same benefits of previous ones, plus piracy tech gives an extra 1500 gold per level. So maxed out an extra 30K gold. So a nice even 100K.
5.-Captain, or Pirate lord-equal to admiral-Same as previous ones, but tail ransom is increased 10%. so a howker ransom is 1100, a Sotl, 82500.
To gain ranks Several missions are offered and X points are needed. Recommended missions can be plunder X ships, Steal X gold, Skirmish X amount of times, and a few NPC missions of hunting down pirate hunters.
Please note that this is all up for discussion, numbers can be changed as can the titles.