I hope you add more to this.
But I had a idea.
I think it might be worth asking peamix he might not mind You using his old world ideas (I’ve seen someone that said they got permission for fan content) it might be a good source of world gimmicks.
mainly the volcano caves.
In a game called oxygen not included (the space colony game.)
Theres a planet that’s extremely hot planet covered in lava that has a rare mineral in it only found in it.
Basically it’s a uninhabitable planet but zombies were sent to harvest rare resources from it so Dave and the player have to stop them before zomboss makes a overpowered weapon.