I'm not sure if this would be something people would want. But i think it could add a new depth and affect current strategies, but create new ones.
Crew on all ships needs to eat.
Lets say each crew members eats 0.01 to 0.1 food per hour.
Ships when docked eat food from warehouse or automatically buy it from market (if applicable)
Ships right before sailing out will load ship with enough food to last the sail (Can add more if we set in settings, lets say we choose 200% to sail there and back, because other port doesn't have food.)
Ships that are sailing will need to have food on board to feed crew.(both trade and war fleets) If there is no food, crew will start dieing at a rate of 1 crew/1 hr
This would also affect profits and travel speeds of all players. Would need some kind of boost in the opposite direction possibly, to add strategy without pissing everyone off.
There could be voodoo made to counter this. (blessing of the gods, 72 hr) All crew members don't need to eat or Gods create food for crew.