I have seen multiple posts around this forum asking for a private island in which you can customize your house and meet with pirates from your guild.
I think that using a private place in the open world we all know won't work as it would break the game's idea of a session based gameplay.
However, How about if instead of loading into the menu we loaded into our Guild's Base? It would be a shared enviroment out from the Sea of Thieves in which you can meet with everyone from your guild and then choose there if you want to set sail into High Seas or Safe Seas.
Technically it might be a hard thing to build as it will change how the game loads (devs I believe in you), but could be a way to give players a hideout without changing the map.
The only issue I would find at the moment (apart from the loading times) would be how this could be hosted in terms of servers or local hosts.
I want to see how do you feel about this. Please post your feedback. Happy sailing.
