I've thought about it for awhile, and I've said it before, the Pirates doesn't have a huge amount of plusses.
So, throughout history pirate vessels were always "able" to carry more cannons than the ship was supposed to have. So I propose that all traditional pirate vessels (Sloop, Sloop of War, Brigantine, Brig, Brig of War, and Frigate) should have 4 extra cannons, when you are part of the Pirates. I thought 4 was a number that gives a greater edge against merchant vessels, and some military vessels, but doesn't make it completely unfair.
Any thoughts?