I think a nice twist on a big pirate ship for a new line would be a model that has two construction modes; just by changing a few features, flags and gunnery placements you could go from a trading vessel to a captured pirate ship for the high seas! You could have a Pirate Captain and a Trade Ship Captain, mutinous crewmen, a hapless Governor and his Daughter included in the set. There should be a nice brig as well as the standard Captain's Quarters, a cargo hold and all the usual decks. I'd like to see a set like this no smaller than the Skull's Eye Schooner (and at least as detailed), but with neutral sails so you can run up the Jolly Rdger when you feel the urge to go Privateer. It would add to the play features, increase collector value and encourage multiple copies.
Add-on sets could be a long boat with crewmen, a medium sized costal fort, a trade harbour, a tavern for wayward sailors and recruiting pirates, a shipwreck island and a fast and well armed Imperial Warship to enforce the trade winds!
I'd be hooked, arrrr!