... I can see a couple areas where the game really could have been more successful in sales.
Sea battles and a full game of combat. The best pirate game would be a combination of Tropico city building with the sea battling of Sid Meiers Pirates and the land battles of a better RTS game. Not so many units like Rome Total War. Just some good pirate and other units in squads and decent fortresses and fighting anywhere it happens to be.
What is proposed is a "god" game with the player hovering in the sky and moving anywhere on the earth. Omnipresent and Omniscient - but unable to control the free will of the NPCs..
Pirates did very few "land battles" other than raids on ports. Given the scale of the game, one or two ships crews would be all that would be involved. The main feature would be house-to-house street fighting. Unfortunately, the code to coordinate the animations of the units and the results would be gigantic.
Watching the sea battles would require the player to leave the island to run on auto pilot. That is dangerous. Pirates were not very good at fleet actions.
It's so easy to "like" pieces of lots of games. It's hard actually to do the logic of putting them together while keeping the necessary suspension of disbelief and some verisimilitude.