I understand that singleplayer isn't a large element of this game,but still. Who doesn't want singleplayer?
Players will obviously still want to play on the server but exploring your own universe is also fun.
The system of crafting and gathering resources could be made easier for singleplayer.
The update system could be something where it is updated when you launch multiplayer and the difference can be seen in singleplayer mode also.
Could we also have a local multiplayer mode also?
Not everyone has a 24/7 connection to the internet for gaming. Most gamers do but others don't have the time download updates and connect to the server to play. They just want to launch the game and play. In this way, the game can be exposed to a wider spectrum of gamers and people.
And also an interesting concept:
Say for instance a player was playing singleplayer or local and then wanted to play multiplayer, they could pause the game, select multiplayer, it loads for a couple and they resume the game, continuing their flight but their worlds/ solar system has faded away and they are now in the multiplayer universe approaching a safe zone which will soon appear in the dark void. I dunno how this will work in real time but it's interesting to think about.