I didn't mean to get people hung up on specifically the term and legal status of "pirate". It can go by other names as popularly discussed. This was just to get the rough concept across, but I probably should have accounted for other names, even if I was going with the name people would know the best out of popular culture and forgot Corsair. Pardon for that. >_<
If the issue is defining it, what I was going off of is based on the popular fantasy of what a pirate is, not specifically "sea criminal". A swashbuckling rapscallion who sails the high seas (or is *associated* with a ship crew) and sometimes uses supernatural powers. Besides, the legality issue could be moot to an extent if they go with the idea popularly discussed on the forums and in-game over the years of it being called something like Corsair, Privateer, or FF5's Cannoneer, like you said. A privateer is a pirate, but a legally sanctioned one, so not a criminal in the nation/alliance they're affiliated with; which is how Limsa Lominsa currently operates as far as I know. They outlawed piracy but still use privateering, with old pirate crews operating now as legal crews and some want to go back to the old ways.
And true, you can't steer a ship at sea in FFXIV, but I still included an element tying into it with my suggestion with having the L3 Limit Break being that you summon a ghost ship to fire on your enemies, if the Job uses supernatural elements from popular ideas of pirates. Additionally one of the bosses of Sastasha (Hard) which gave me the initial desire for a Job like this and what weapon type it'd have, you never fight them on a ship at sea, you fight them on some form of land despite being a pirate.
Personally I would be MORE than okay with them making it Corsair (like others and I thought Viper would be from the trailer for Dawntrail), if not another name like Privateer, Cannoneer, or something entirely new. I think I picked a bad term to open with.
Edit: I forgot about Rogue. Where does that fall then if the class and its lore/guild in the game are criminals and also operating out of Limsa?