My son is thinking about running a pirates campaign using our Mythical Journeys system.
THIS IS SO COOL because he's never wanted to run a game before! He ran one session years ago and didn't like it.
But Mythical Journeys is so laid back that it almost insists upon people wanting to pick it up and play.
Here are some ideas he's brainstormed:
Magic guns with ammunition with poison, or ice, or fire or whatever
Pirate class kind of like the 3.5e Ranger, where you can choose whether to be really good at shooting sidearms, or really good at using swords (or be a generalist and be adequate with both).
Necromancer pirates and Necromantic magic items.
Armor classes based on something other than platemail, for instance, because it's too heavy to wear at sea.
Monsters including the British Navy and monsters inspired by Pirates of the Caribbean movies and the Assassin's Creed pirate game.
Exploration of islands at sea.
Before my last big hard drive crash, I had a ton of great resources for generating instant island inhabitants, but I don't have that any more. Maybe Chris Tamm has some? Or maybe in Mazes & Minotaurs. It seems like there might be something in M&M.