Everyone is saying that the biggest issue with the game is that theres no reason to get as much gold as possible after a certain point. I agree, and I think a great way to fix this would be player housing. Make everything crazy expensive, so once you have your outfit and other ship cosmetics you still have something to play for.
Make it an instanced area that you have to sail off the map a certain direction to enter, you park your boat in front of your beachfront property like some sort of Miami style neighborhood. This could be the safe zone everyone wants and you can meet people in town and show them your house and all the cool trophies and decorations you have worked hard for.
