How about adding a lifeless planet type? Yes, there are the moons but why not a full planet as well? By "lifeless" I mean no oxygen, no animals, and no plants. Otherwise it could be as lively as you want from environmental stuff like lava and volcanic eruptions to frozen ice lands to wastes bathed by radiation. POIs could spawn there, too, or at least those that would make sense on an otherwise barren world. Having it as a planet would allow you to offer it as a starting world, too. That would be a different kind of challenge, starting from the problem of how to get oxygen when there's no atmosphere for your o2 condenser. Probably would need to mine ice and/or scavenge wrecks. After o2 you'd need to find food and then somehow make ammo etc. Would also be quite natural as not every planet in the galaxy ought to be habitable.
The Vanilla game will not have them in the near future but if you decide to play a Scenario like Project Eden you may see your wish become true. You will find Dead Planets - no Air, no Life, no Plants - recreating different causes, like nuked, Climactic Catastrophe or.. other reasons. Those Dead Planets are in P.E. indeed Starter Planets but can be found in the Galaxy as well.