Ninjas rely on stelthy, silent kills. Pirates use yelling and intimidation before they charge. There is no way to add these together. Same thing for the weponry. Ninjas like I have shurikens and katanas, along with other lesser-known impliments. Pirates use scimitars, which are actually fairly similar to katanas, but the sidarms they carry are far to loud to be carried by any self-respecting ninja.
Do you guys just know both fighting styles, and use them when nessassary? If so, how you handle the different outfits. If not, the same question is there, is there any outfit? Some black of pirate regalia?
It seems to me that you're emphasizing the differences rather than the similarities. But you are right, some parts of the fighting style are different. But that's not all. For me, the breakdown is such: My fighting style is very Ninja, but my lifestyle is very Pirate. Does that help?