Love the game, love playing with friends a whole bunch! I play the game solo sometimes, and feel it would be really cool if we were able to come across an island, and find a "survivor" from a boat crash from time to time, and hire them as part of our crew.
For example I burn the food, or forget to cook it, wouldn't it be nice to hire that NPC to cook your food, and store it? Or help lift the anchor, and raise/lower the sails, maybe you want him to be on a cannon (or in a cannon lol) maybe hang out on deck and wait for players to board ship! Also be able to hire a bunch more you come across.
To keep it balance so one ship isn't incredibly op everyone has the same amount of crew I'd do one NPC for each task: food, sails and anchor, Cannons, or harpoon, deck, or lower deck (lower deck would protect treasure if that's where you store it) NPC's can never steer the ship! once at a outpost you can have them help you unload your treasure and they'd walk it to the spot and help sell it. Also once there you can go up to them and relieve them of their duties for blue coin.
I'd make it to where they can die obviously but, so they're not OP I'd give them slightly less health than a normal player, which can contribute to a happiness meter. The better health or "wellness" you keep your NPC's the better they'll perform tasks and the more blue coin you get from relieving them of duty. For weapons idk maybe just a sword because NPC's in the game are really good shots lol. That would be if this ideas even taken into consideration. Alas yarg me mates I'll be seen ye again! Lol 😂😂