Maybe in a Sea of Thieves 2 which would be built on Xbox Series X2/PC architecture it could happen.
But as of right now: It can't happen.
Sea of Thieves is built from an older build of the Unreal Engine. Due to the level of modification of it, it can't be upgrade to Unreal 5... I would be surprised if there aren't programmers at Rare working on making a next gen version of Sea of Thieves using the most recent build of Unreal... or even working with Epic to have some of their innovations built into the engine itself.
But because SoT being built for Xbox One architecture, it can't be expanded too much.
If you take a step back and think of ALL the complexities SOT has over other Unreal Games, it makes a bit more sense.
You are a pirate, standing on an island, and you have a pistol that shoots a projectile: The game basically acts like Fortnite: it calculates your position, trajectory of bullet, the movement of your target, etc.
Now you are a pirate standing on a boat in choppy water. That boat is now moving up and down on the WORLD Z axis, and tilting on all SHIP X/Y/Z axis. Depending on your position, your position is now moving in WORLD XYZ axis, AND you can move in the SHIP1 XY axis of the ship deck... shooting a gun towards an island with a person moving in the WORLD XY Axis on the island... that massively complicates how the game calculates things.
Now you are a Pirate Sailing on a ship, moving in the WORLD XYZ Axis, Surrounded by 5 other ships also moving in WORLD XYZ Axis. Each of them is rotating in the XYZ Axis of their SHIP, and they have 2-4 pirates moving in the XY axis of the SHIP.
Due to the complications of all those calculations, they had to limit the number of ships (6+1) to the server AND limit the number of players(16+?) to the server. (The pluses are the number that can be added temporarily for an Hourglass Battle... not sure if the servers can add 4 players for a 2 Galleon Battle)
If they added a 5 person ship, that would leave only 11 player slots left on the server. 3 brigs and 1 sloop, or 2 galleons and a brig. If there were two 5 person ships, I would realistically only have 2 additional ships on that server... which would make it feel very empty.
Hopefully in Sea of Thieves 2, we can have more ships, more islands, and some bigger ships, but that is going to be several years away.