Firstly, I know many have suggested a personal island or hideout in the game before, with many not getting the point of no safe place in Adventure.
So what I propose is a hideout that's separate from any mode, selectable from the menu, perhaps acting as a back drop for your pirate in place of the current one.
You (obviously) cannot bring loot to this hideout and there would be no way to access it from within Adventure or Arena, you have to leave a server to access it.
In this location, you can equip your pirate cosmetics, check your My Pirate progress and display some unlocked items (favourited) on the wall, including certain titles as "trophies".
There could be a "newsletter" on a desk or side table, updated with news from the seas (the sort of thing you get in the Mysterious Notes, plus other relevant information)
Looking out the window here, you can see (but not access) a ship moored on a dock - perhaps you could even choose your favourite outpost? You can also customise this ship to your liking as a backdrop.
This is intended to be a personal space for your pirate, without impacting gameplay, but also to give more reasons to unlock cosmetics so you can customise it to your liking.
