Here's my proposal:
At grids Q-22,23 / R-22,23 is where all dive only HG battles will take place if players have a captained ship and a Bilge Rat Trinket, purchased from Larinna. The trinket goes permanently on your voyage table, next to the HG. When you vote on your faction and the dive map pops up, the trinket will glow and if players want, they can turn it off, but it will be on by default. Having this trinket active when diving will have ships surface at the aforementioned grid coordinates. This area will be surrounded by partially sunken ships, rocks, and chains, along with a very light fog just at the edges that creates a barrier from other ships outside it. So far, I've come up with calling the place "Uncharted Wrecks" but I'm open to better ideas, which I'm sure there is plenty.
Broken/half sunken ships and chains connecting them will finally allow players to not worry about being blundered off their ships and having it sailed out of bounds and destroyed. Ships ramming sunken ships in the main game do no damage, so having this incorporated would make a good visible boundary for an HG battle, without worry of players taking over ships, ramming the edge and trying to sink their opponents that way. Too long, the meta, especially for solo sloops, is to board, and sail out of bounds while blundering the opponent off their ship.
Third party players can't get past the barrier unless they cannon over it.. So, hypothetically they could try and cannon over to sow mayhem, but they can't bring their ship into the battle.
At 10 minutes, a bell sounds in the distance notifying the players that they have 5 minutes left. At 15 minutes, the ship with the most points wins, unless one is sunk before hand.. farming pts will have to be part of it because I don't know of a way to stop players from doing so, but doing these methods to farm pts won't increase your faction XP after winning the match, so sinking a player ASAP will still be the best method to gain levels quickly, not sitting and spawn camping for 15 minutes. The time limit also doesn't need to be involved. I would just personally like one.
A destroyed "garrison" area will exist in the dead center of the Uncharted Wrecks location. It will basically be an accessible platform of sorts that has a few barrels of supplies on each corner, and a place where players can TDM/1v1 if they really want. For example, you can find people that dice roll for wins or losses in HG, so if players did something like shoot off flares at the start, they could potentially know they want to 1v1/TDM in the middle and they could pull up and just fight each other for 15 minutes or until whenever. If both crews interact with/vote at the obelisk in the center of the destroyed garrison, then when they die, they won't be sent to the Ferry, but will instead remain in a revivable state until the respawn. AND both ships will have their cannons point upwards and glow purple, like they've been hit with a skelly cannon curseball, for the remainder of the fight. This can ONLY happen if BOTH crews vote at the Obelisk at the destroyed garrison.
AFTER the battle, losers will be migrated to a different server and winners will have to option to dive for a new battle or they can lower their hourglass on their ship which will make that crew dive and surface near an outpost to sell their flags if they want.
Players who deactivate the trinket on their voyage table can still do old style HG matches that have them appear in random areas on the map and play HG how we've done from the start, whether that be invading players or whatever. This NEW trinket or whatever it ends up being is a way to put HG players in a specific spot that can be safe from third party players ships, has a time limit, a place to use weapons only if both crews decide, and crews won't have to worry about their ships being sailed out of bounds, AND they can dive to an Outpost or another battle INSTANTLY after their battle if they choose.
What did I miss? Let me know if you like this or do not like this. Also, I get that Rare has a laundry list of other things to fix, so please don't bother mentioning them. This idea is my "want" for HG if they had the resources and time to make something like this happen, not dependent on anything else happening with the game.
P.S. Kegs will also not work at these grid coordinates, so third party players can't somehow bring a rowboat loaded with kegs and somehow cross the barrier.
