I have a few ideas. First of all, though, I absolutely love the art and style of the game. I can't wait to see it as it develops!
1-Multiplayer/Singleplayer Screen: I would like to have a choice to join a single or multiplayer game as soon as you launch up. This one's pretty short!
2-More star systems: It would be amazing to be able to build a ship and travel throughout the stars with companions. Each one could be similar to the next, but with different planets. (Maybe see Starbound and No Man's Sky for what I'm talking about.)
3-More planet types/add planet types: Going along with the previous suggestion, specific planet types could be cool. (I.E. Magma/Ocean/Forest)
4-Flora and Fauna!: Plants and animals would be neat! Maybe only on specific planets. Also, I WOULD LOVE TO HAVE ALIENS! Yes, aliens. Like UFOs. I think that could be really cool. Not hostile, just cool ships flying around the universe. Maybe you could have a friend come with you on your travels in singleplayer. I think that they would fit with the style of the game well.
5-Ships: I mentioned this before, but a small, multi-personnel ship could be neat. One with not just chairs, but a cockpit where you can walk around in. I realize that there's already a small lander craft one, (and maybe you could dock the lander in the interstellar ship,) but a larger one could be neat.
6-Mechs/railways: Some way to easily and quickly transport large amounts of items could be cool as well.
7-Customizable Characters: I really want to make my own space suit. That would be amazing.
8-JETPACKS!: This could be a cool way to easily travel around the planet. Jump/jetpacks could be great in this game.
Some other topics I agree with: