The more I think about it, the more it grows on me with making the outposts as "safe zones". Allowing the open waters and other islands to be spots that you can be attacked on. If we are going into some form of realism and even in fantasy here, there were islands where a sleuth of pirates gathered that was considered, in a way, a " safe zone". Sure you could get in bar fights and gamble and get drunk, but there was no sort of stealing allowed, and if it happened and you get caught, the pirate that got robbed put a bounty on your head... This get's me thinking and wondering and get ready for this because it probably would never happen especially with the game coming out in a few months. What if someone could try and take your loot in a "safe zone". Why it would just be sitting on a ship for that long idk, maybe it's during the process of transporting and turning in the chests. No shooting down of ships, but they could steal, and you'd be limited to one chest every individual ship you find every 24 real time hrs. The person or crew that took it would have to take it to another outpost that wasn't the one where the original ship was. There would have to be a cool down for that chest as well because that would allow enough time, ideally, for the original owner to realize it was gone and to put a bounty on the thieves. The owner can also follow the thief and stop them before the time runs out.
Now to prevent the thief from just being able to sit at another outpost as the time goes down, which would prevent the original owner from killing the thieves, each outpost is armed, heavily, with PVE cannons that would almost immediately destroy your ship upon entry before even being able to carry off the chest to sell it and it won't miss. The only way to be able to successfully enter the next outpost is by waiting for the cool down to go away. This cool down should be enough time to allow the previous owner or another crew wishing to receive the gold from the bounty to put up a decent fight before being able to sail in and turn in the chest.
How would the PVE be able to know it has a bounty? Each ship would need to be equipped with a small space ( maybe just make the entire captain's quarters this space) to be able to store chests, originally gathered by your own crew or stolen, they would be placed in here. once the chest is dropped in this location on the ship it gains a form of a tracker on it. When it is YOUR chest it will glow a very welcoming color so it is obvious it was not stolen. If stolen, it glows a harsh red, also engulfing the entire ship with a red hue that won't go away until the cool down is gone. This hue is also trackable on the large map on the ship. This allows firstly, PVE to register that this ship can not enter an outpost yet and if it does it will be destroyed. Secondly, it allows PVP players to be able to notice that it has a bounty on it and if destroyed you will gain an amount of gold for recovering that chest and turning it. If you are going to turn in the chest for a bounty you can't put the chest in the holding area with your other chests. it must just rest somewhere else upon your ship to turn in. Putting it in your holding area will start another cool down immediately designated you a thief, allowing more time for the original owner to track it down and take it.
Before getting into more rules all of this should be an option that can be accepted or declined. the owner would walk into the captains quarters where the designated holding area is for chests and there would be a note stuck in the wall with a knife, it would be glowing so it's obvious, stating "a chest has been taken, would you like to recover it or let the thieves bask in its spoils". You can either decide if you want the hassle of going and tracking it. Putting a bounty on it for an amount of gold that you personally put up for it. Or just letting it go. If you let it go, the red hue immediately disappears and the thief is free to turn it in with no hassle.
Chests can be stolen from thieves, but there will be a full restarted cool down as soon as it is placed in your chest holding area. While on an outpost island, chests can only be taken from the designated space on the ship never from the hands of an original owner while they are walking with in an outpost ( this is not the case while exploring outside of a "safe zone". aka: outpost). Players are notified when a ship turns in your stolen chest as well as if it was recovered and which outpost it was dropped off at and if a new thief has taken and the cool down reset. If you recovered the chest and are owed a bounty, an NPC ( that's the same at every outpost) at an outpost will give you the bounty upon returning the chest to him. If it is your chest, you will have to travel to that outpost that it was returned to to recover it. you can immediately turn it in upon recovery. If you put a bounty on a chest and the chest does not get successfully returned, your gold is immediately returned to you or carried over to the next thief if applicable. If no one recovers it after the thieves ship is destroyed, it fades into nothingness. Bounties have a minimum payment of 50 gold with the maximum limit of however much you own. If you have less than 50 gold, you can not put a bounty on the chest, your only option is to follow it yourself or not go after it ( this allows a risk reward for everyone involved. you could put a high bounty on a chest to then open it and only receive a fraction of what your bounty was. Bounty takers could receive only 50 for a lot of work but could also receive hundreds of gold. The chest the thieves grab may not have a lot of gold.)
All of this can have reputation, giving you the opportunity to buy certain attire, sails, gun skins, ship skins, so you can be notoriously known as the greatest thief of the sea!
