Developing a video game would be nice

I have had a couple of ideas in the past about a video game but this is the idea I’ve recently thought of: I want it to be about pirates and stuff. You start off designing your starter ship which you can upgrade later in the game. I don’t really want to have a set story, I’d rather have the community make one up, assuming the game gets any attention. You slowly build your crew up or make upgrades to your ship by maybe completing quests. The actual looting system would be by completing quests or finding them in the ocean. I feel like a problem I would run into would be keeping the game exciting because for most of the game you are at sea finding gold and stuff. I think there should be islands that you can explore with a lot of wildlife and treasure. There should also be monsters you have to fight. I also want there to be colonies and land you could claim. I could make it an online game but I don’t know how that would work. Any game design or coding suggestions/tips would be greatly appreciated.