At its current state, Astroneer only has a handful of planets. Arid, Terran, Barren, Tundra, etc. While each planet does represent a different difficulty of survival, I think that it would be nice to expand the horizon of planets, and make the astroneer universe much much larger. A few ideas to keep in mind whilst expanding the galaxy:
Add black holes
Add planets with asteroid rings and different weather
Add possible abandoned space stations to loot and repair
Planets at the far reach of the galaxy that contain an abundance of rare resources
Dwarf planets
Multiple