Sooo what are the essential features a pirate class should have? Think of it as being a 3-level prestige class or an abbreviated paragon path or something- condense down to the essence of what you think makes a pirate, a pirate.
The defining trait of successful piracy is speed, although deception and use of cover is sometimes necessary to get close enough to pounce. Surprise is his most potent weapon. Additionally, fleeing the scene and staying ahead of the large gun-laden government sponsored patrol ships is a priority.
A proper pirate (as opposed to some guy on a pirate ship who helps proper pirates rob boats) first and foremost must know the difference between a topgallant and a jib, or which way is "starboard". He can climb rigging and fight one handed from it. He knows how to sail a ship and make it move very quickly. He can read weather conditions to know when it will favor his ship over his prey. Eventually he may learn to navigate by the stars.
Moreover, speed means he must move with an economy of mass. He can judge very quickly whether an item is valuable enough to weigh him down further. He doesn't like to wear armor and has developed other means to defend himself, but mostly relies on speed (i.e. running away from tough guys, and catching up to the weak). Traveling light also occasionally means survivalist improvisation: knowing which nasty tasting blue crabs will kill you and which will kill your hunger, and which coastal sands to dig in looking for them.
Over his career as a pirate, he is likely to at some point notice a secluded bay or cove where passing traffic would not take notice if a small camp were set up occasionally. This is his Pirate Cove, his secret stash and hide out spot. A good pirate has many of these and his knowledge of them comes to define his status as a savy pirate.
Nicely done, too! But this isn't actually for 4e, it's for my homebrewed system, which rolls a lot of the design space for advancement into narrowly focused, 3-level prestige classes. So I'm trying to figure out what the most "piratey" pirate stuff is.