Imagine an island for your guild. Perhaps when you choose to travel to your guild island, you are similarly phased in with 5 total guilds and their islands. Your island starts with nothing. You must sail with guild mates to nearby islands to get wood and supplies to build up your island. As your guild mates turn in missions and get achievements in the normal game, each mission completed earns the guild some separate currency only used to buy guild island decorations, etc.
Ultimately you’d be creating an area for guilds larger than four players to all get together and meet. You’d also keep a sense of danger of exploring nearby islands for building supplies with other guilds potentially doing the same. Other guilds could also dock at your island so you could show it off.
Guild islands would be an awesome social element, even at a more basic level to have a place for more than four friends to meet, drink grog, socialize, and pick out their crew.
