There’s one issue with multiple players that I haven’t worked out how to deal with yet.
The problem is, the game engine does not support having players very far from each other. The maximum allowed distance is about 4000 blocks, and I could make it up to 16000 if really needed, but either way it is finite. At some point, if players keep walking in opposite directions, there will be trouble.
From the gameplay perspective this is not a big deal, because having players so far away from each other is pointless. It essentially degrades the game to a singleplayer game, as players cannot interact with each other without walking back for many days first.
However, there needs to be some mechanism that prevents players from going too far from each other and breaking the game.
“Hard wall” limit is simple to do, but has a major drawback. If one player started to build something, the other player can screw it up by just walking in one direction. At some point, the first player will no longer be able to move away from the 2nd player and parts of his build will become inaccessible.
If you have a better idea how to do it, please share in comments!