Proposal
I suggest to add additional upgrades to the Captain’s Quarters. Each of these upgrades must be bought separately from the ships they would apply to, and if the upgrade can apply to multiple ships it will. For example, upgrading the bed on the Brig would unlock that upgrade for any ship that has a bed in the captain’s quarters.
Details/background on your proposal
Whenever you unlock your first ship with a captain’s quarters (likely the Brig) a new tab unlocks in all Builders- Upgrade. At the Upgrade tab, you can choose an eligible ship to see what upgrades that ship can get. As mentioned, if a single upgrade is listed under multiple ship types, buying it once buys it for all of them. Upgrades usually cost Galleons, with some also costing other materials, or requiring you to acquire blueprints through quests or sealed chests. Some upgrades have mechanical functions, while others are purely cosmetic. Here’s a basic list of what I could think of:
Mechanical
Silver/Gold Trimmed Cooking Pot/Cauldron
By trimming the cooking pot or cauldron with silver or gold, they slowly but surely generate the same magic that causes silver and golden variants of those crafting stations in the Dark Sea. Once per day, cooking or brewing something in these crafting stations will make them as if they were made with a silver or golden variant of that station. Can be upgraded further to allow two or three uses per day, with the cost scaling up over time.
Edit: Two things: First, in order to unlock this upgrade you must have used a silver or gold crafting station enough times in the Dark Sea in order to access them. Second, an alternate effect for this upgrade is to give you extra uses of pre-existing silver/gold cauldrons. One extra per station you find, up to a daily limit. That would remove the problem of removing an incentive to enter the Dark Sea.
Bookshelf Modifications
You are now able to store and retrieve copies of books you find on your adventures. Books obtained through the story (such as Morden’s journal) are automatically stored, so that you cannot permanently lose them.
A secondary upgrade would also allow you to bind treasure charts to the bookshelf- start at one and upgrade up to 3. A chart bound to the bookshelf is not lost when you die or leave the game.
Vault
Installs a small vault (on the Brig this would be beneath the desk) that can store a small amount of Galleons or a couple of items. Items in the vault are not in your inventory, and thus cannot be traded or sold until you take them out. You can also access your clan bank from the vault. Upgrades increase the storage capacity, to a maximum of 15k Galleons and 20 item slots.
End Table
Adds an end table somewhere in the Captain’s Quarters (or outside of it) which always enables you to place a brew or large meal onto it, regardless of ship tilt or current HP. Items placed on the end table never despawn, and are saved when redocking or server hopping. Potential to add anywhere from 1-4, with the cost going up for each new one.
Cosmetic
Bed Shape
Enables you to change the appearance of the spawn bed. Examples can include a bed like you would find in a fantasy princesses room, or a hammock, or even just a beat up couch. All beds would also have their own candles.
Fish Tank
Enables you to change the appearance of the fish tank. Examples can include replacing the aquarium with multiple smaller fish bowls, or changing the trimming as well as the internal decorations.
Desk Clearing
Clears unnecessary items from the desk by the cauldron, and in its place adds extra picture frames.
Bulletin Board Clearing
Clears the bulletin board, allowing you to replace it with 1, 2, or 4 spaces for pictures.
Gemstone Rack Expansion
Increases the size of the gemstone rack, adding a slot for all of the exotic gemstones.
Carpet Patterns
Changes the carpet, giving it a new pattern or shape. Some designs might also remove the carpet entirely in favor of a floor with a unique material. Other designs would also have more colorable parts for the paint brush.
More Money Piles
Exactly as you would expect. Spend money, add in more money piles. Some piles could also have you spending gemstones to add those in too. These piles are in addition to the normal ones that show up if you have enough money on your person.
Reason to add/change
Quite honestly, when I originally heard the brig would have a customizable captain’s quarters, I expected more to it than just the picture frames, gem rack, and fish tank. With this suggestion, I aimed to make more options for customization while also adding in a few extra mechanical features I thought would make sense for the captain’s quarters.