Capturable Fortresses, Fortress territories

(I highly doubt this would become a thing, but I just wanted to put my idea out here)
Fortresses by themselves are cool and all, but if when you defeat a fort you get the option to claim it, thus creating a small territory around that fort. Owning a territory grants you many benefits such as raising your ghost fleet in order to defend your territory. In order to do this, you have go on some type of voyages to return gold back to your treasury, where you will then be able to upgrade your fort such as more supplies, stronger ghosts to defend, and eventually a small fleet that can patrol around your territory.
It can get even better than that. If you capture all forts in a region, you will gain more benefits such as a larger fleet to defend (Think of the board game Risk when you control a continent).
If two crews have territories in the same region, they can battle each other for those territories either with just there own ships, or bring along their ghost fleet. (Note: These ghost fleets cannot leave their respective territories)
A limitation would be that a single crew cannot control forts from multiple regions, so it would not be possible to control the entire map. There could possibly be alliances between crews that each have their own territories.
I understand this is probably game changing, but this is just an idea that I feel can add some new life to the game.