That's a bunch of pebbles.
A captain was as important as a ship name. If anyone held the "ultimate" power in a pirate ship that's the Quartermaster. He's the doing doing the split for shares and being the ultimate crew representative.
Captain has the ultimate power during chase, pursuit and combat. Outside of that everything is brought to vote - where to go, what to steal, where to sell and to whom. In some cases the old dogs and specialists, like navigator, linguist and obviously the Quartermaster will act like "praetors", being the "head" of the council and representing the diferente ideas aboard. That's the only comparison you can make to "Romans" ... lol.
In the case of consorting and having several ships working together it was by renown and not by rank, so ultimate command of a fleet was given to the ship with more renown and only second consideration to the pirate captain.
There's a lot to say about pirates but the only sure thing is - they wanted as much distance from the maritime and navy tradition they chose to abandon as much as they could, especially after 1713.
( plus you are looking only to anglo.saxon pirate tradition and forgetting they are only a small part )
The only rank truly necessary for NA is Captain or the ship name. If anything, renown, by plunder.