I don't agree with the idea of making worlds PVE or turning off combat. Yes, this is SOT and yes people should be allowed to steal and attack. It's the threat of these and the requirements to avoid it that make some of the highs of this game so good.
However. Trolling is a problem. It serves no purpose, it is not fun. The act of trolling isn't even fun for the trolls - only the result of denying other people their fun. Not only is this not really accurate to the pirate life, it's clearly against the spirit that Rare is trying to enable. Right now, there's no penalty to trolling. There are no negative consequences whatsoever. In fact, there are only disincentives to following the pirate code. That seems a bit backward. So how can we change the calculus?
My first thought is bounties. Bounties that can only be called against players who have killed you repeatedly: targeted, not random. As this bounty goes up, the danger for the person goes up. First, their bounty gets displayed next to their name. Then, when it gets high enough, they get the equivalent of the Reaper's Mark put on them (the player themselves) with their bounty total right on the map. Chase em down for gold and glory. Not only does this gamify the act of retribution, it makes it risky to keep trolling. Everyone know where you are and can avoid you, and your bounty only goes down when another player kills you. At the same time, this could be a legitimate point of pride for crews that just want to PVP. They've got a huge bounty, but they still get away!
But there are two problems: 1) it can be gamed. Get two ships and they can just "farm" bounty level and 2) it still relies on other players to actually kill the player, which is hard when no one else wants to even engage. 1) can be solved with timers and cooldowns, essentially.
But 2) requires something deeper and more integrated: world responses to bounties. As in: what if as you cause more havoc in the Sea of Thieves, the world automatically and invisibly starts to move against you. First, what if the game invisibly tracks your PVP aggressiveness (we have this tech from Arena already) and contributes that to your bounty total behind the scenes in addition to other players actively adding to it. Then, at a certain level of bounty again, enemies start spawning. Again, to provide a risk to this gameplay style that currently doesn't really exist now.
First, you see more megalodons. Behind the scenes, their aggressiveness toward this specific ship is amplified. Then you get skeleton ship spawns out of nowhere. And at a certain level of bounty (before the getting on the map thing), you get a special gnarly megalodon that is extremely large and aggressive and ONLY targeted at ships belonging to pirates with high bounties. So this will be a very specific thing that will prevent troll crews from being effective in multiple ways. BUT, it's actually still kind of a cool thing for crews that just want to be aggressive. They have to balance how much they go out and attack people or risk being sunk. They have to take breaks more often to turn in stolen chests and the like. And they can farm these creatures if they want to for the meat and loot. Again, these are all good because they give benefits to the aggressive players for doing things OTHER THAN killing people while actively preventing them from griefing in an in-universe way.
I think this solution maintains the threat of PVP, maintains the joy of playing PVP for those who want to, but also makes it challenging to play only that way. It doesn't take away the threat of other players from those who want to PVE, but it gives you some tangible responses to them that don't just boil down to "git gud".
Dang I wrote a lot. Oh well. Long and scattered thoughts. But I wanted to share them. I'm sure others have come up with better ideas since.