Story: A new group of islands has been discovered in the 1500's. You and your ragtag group of pirates must act quickly to gain control of all the precious resources on these islands. You start with a small group of pirates but slowly build an army of skilled workers and fighters.
Gameplay: Many RPG elements will be involved. Hiring and training your crew will be the key to success. Harvesting resources, building ships and towns, and training soldiers are all abilities that take time and money to do. Being able to do this while fighting your enemies is important. There would be two modes. The management mode, where you can manage resources, create trade routes, and position ships. The second mode would be where all the naval battles happen. The fights would be in a 2d isometric view, with wind playing a role in how you can move the ship.
Technology: Most 2d game engines could handle making this game. An online leader board might be fun so you can compare how much gold you have with other people.