I am writing from point of view of a level 8 captain, it is possible some of my points get 'solved' by getting access to game features restricted to higher ranks, who knows.
Fleet ships need some improvements:
(1) why does it happen captured ships in your fleet have vanished when you log in later? Sold? Escaped? It should not happen.
(2) we should be cable to put player-crafted ships into fleet as well (with risk they are lost once sunk, like NPC would)
(3) we should be able to offer captured fleet ships on auction house for sale, not just breaking them up
(4) we should be able to switch ships and sail captured ex-NPC ships ourselves, (that would include our own ships change into fleet instead and become vulnerable, that is okay)
(5) we should be able to use NPC fleet for cargo transportation. Give us access to their hold. I am surprised that is forbidden now. This is one of the main purposes of fleet ships besides combat assistance.
(6) we should be able to equip NPC fleet with guns of our choice, maybe even upgrades. And fill up their partly depleted crew, of course.
These changes could mean trade war will become meaningful, even for pvp. Imagine players suspect the precious cargo is on someone's fleet ships rather than the leader, so they focus on capturing his fleet ships instead. Or a group operates in such ways they distract the leader while others take care of capturing his trade convoy ships.My main concern however is solo player improvement as described in points 1 - 6.