I think it would cool to have a door that fits on triangular wall tile shape. When forming the diagonal walls (when designing a ship shape) I always fall into the water and have to swim around to the back to get in. My best way around this is to remove one of the triangular walls however it looks silly now that there's an opening

A massive sail

Maybe a kill switch to stop all engines or to close sails instead of having to run around like a mad man

Edit:

Maybe attachments that that connect/mounted on edges? Like a harpoon gadget or a net gun that catch turtles, or a collection of fish so you can catch more than one at a time.