Just brainstorming upon a suggestion that has already been posted - an idea - what if there was a bit of a twist on the ghost fleet card - instead of gaining a fleet you could use to attack others, what if a random ghost fleet would appear, that if you attacked and defeated, you would gain a prize ship, similar to becoming a marquess - only these prize ships could be souped up pirate ships, like a level "11" frigate, sloop, cutter, LM, Galleon, or a some such.
This would have to be a rare card - 18 - 25 credits to use, with a limit, say 1 hour active, or three to five attack opportunities.
It could be card that can be stacked - perhaps up to four or five. One card would provide a prize of the first three ships (howker, slopp, cutter), a second card would be the next 3, a third card, the the next three. This would allow new players to gain some souped up ships in the beginning, and more experienced players to come across some unique collectible vessels to add to their fleets.
It could be limited to all but the top three, or it could include them (the Flag Galleon, the Large Frigate and the SotL.)
Make the card only available as an exchange card - not available in the witch hut, to help keep it rare and fair.
This may be a way for pirates to do missions - and it may work better once the new ship feature is launched.