So i really like your game, playing this with friends has been a very relaxing and alround fun experience, i think you have a golden formula of gameplay on your hands right here but right now the main thing that seems to be lacking is the end game. Exploring the world and making your raft better is nice and all but it won't stay fun forever.
I think i have thought of a pretty good solution for this problem though. Now disclaimer: i know nothing of gamedesign or the technical capabilities of your engine so if the things i'm saying are actually borderline impossible ignore them i guess.
When i played this game for the first time i couldnt shake the feeling that it was kind of like sea of thieves but way WAY better. So i started thinking about how good a game could be that combines the best elements from both.
I will now try to describe the gameplay experience for a new player the moment he and his friends download and boot up this game.
1. Building a raft. This stage would be really similar to the gameplay as it is right now. You load into a singleplayer game with your friends and you just start collecting stuff to build up your raft. on Islands you can find weapons and you have a map that fills the places where you have been(would be nice if you could name places you discover yourself on that map). after a bit of exploring you find a corner of the map where there are a lot of enemies, obviously you only want to go there once your raft is trong enought to take them, so for now you keep exploring.
2. going PvP after some time you and your friends have built a pretty strong raft and you feel confident you can take on that area, a boss fight ensues. if you manage to beat that boss your ship is repaired and you are teleported to the next world, this world has better loot to make your raft even stronger, it has some ai that bother you every now and again, but most importantly you are playing a PvP game now!!. Just like in sea of thieves you will have to watch out for enemy ships who will try to fuck you up all the time to steal your cargo. Now i'm thinking the destruction of your ship will make your ship reset completely to what it was when u entered that area. The endgoal in this area should be the same as in the first one. you beat a boss to progress to an area with even stronger ai, even better loot and even stronger player controlled enemy rafts. this system of progression could also be used as some kind of ranking system where that first world is unranked, the second bronze, the third silver etc. this will make sure this game doesnt die like sea of thieves because there's no progression.
I think this system could work really well especially since the downfall of sea of thieves was that nothing was customizable except clothing which made it hard for me to really care about my ship. whereas in this system, you and your friends will have build your ship with blood sweat and tears and you will want to show the world shes the best and reach high elo with her.
of course this is a very rough draft of my ideas for this game and i would like to hear from you about why you think it can or can't work.
regards and kisses
Abe Wichers (email@example.com)