I'd like to preface this post by saying that I am happy with the majority of additions of content to the game. I have played Sea of Thieves for a few years now, sometimes grinding, sometimes just enjoying the game for what it is- which can be extremely relaxing.
I have a few friends I play with, but the new Captaincy setup (as it stands) is slightly disheartening with the way ship ownership works. I think something that would have a great effect on players is to have groups of pirates be able to form "Fleets". That way, a set group of pirates can take the same ship out: hear me out.
If you can give 10 guys/gals access to the same ships, then they can all work on the same ships and lessen the load (per person) for ship milestone increases.
This could be handled however felt the fairest- possibly limiting the number of captains per ship based on size (4 for a sloop, 9 for a brig, or even 16 for a galley).
I really enjoy this new update and SoT in general, and I want to say a lot of us are a bit dismayed by the milestones (I've never actually posted on forums before, and none of my friends have either). I think the critiques are largely fair, especially with the math being done regarding 'perfect situations' in the game.
I think this would be a step in the right direction, as it promotes gameplay with friends, and it also lessens the load on some of the ship-specific upgrades.