I kno, lots of peopel already suggested the idea of customizing your own ship, but these are some of my own ideas.
Buying more items for your ship- I think, if POTCO ever adds the idea of customizing your own ship. I think you should be able to buy items for your ship, like maybe another cannon? Or a decoration like rum barrel

.
Captain's Den- Wouldn't it be amazing, if you had your own little private quarters on your ship where only you can get in, unless if you allow others to come in (Like privacy settings). And what if you could also add items in your quarters. That way nobody's private quarters are the same.
Item-Manican/Model of yourself- What if you items were made into the game? Wouldn't it be great to have a 'Model, or Manican' of yourself of yor ship. I would love that, it would feel like having another me on my ship.
Homes- I rember other disney games have this. I know we have a ship, but we need a house from all the salty sea air, and the sea sickness.
Tell me what you think of my ideas. I hope you like them!
Z the Pirate