So this came to me today while I was daydreaming about factory layouts instead of working.
Start with this speech from the lady AI a short while after you complete the build of the space elevator: "Now that you have started your base of operations, I would be remiss if I didn't tell you that the atmosphere of this planet is highly toxic. In order to motivate your production, doses of the treatment, Paracyclodine, will be made available upon successful delivery of specified goods via the space elevator. Should you miss your delivery goals, you will slowly succumb as the planet's air turns your organs into liquid and causes your eyeballs to explode."
So, the idea is that random deliveries are made via the elevator, and in exchange, they send down some doses of medicine. Run out of meds, and you begin to suffer physical effects (health loss, movement slowing, decreased ability to jump) eventually resulting in death.
The items that the corp demands are random, but never the items required by the elevator for tier advancement and always something appropriate for your current tech tier. For example, they may demand 5000 screws, or 500 bags of concrete, or 2000 Caterium ingots, etc. Maybe even multiples (Send us 300 motors and 1500 encased steel beams!)
Once delivered to the elevator, it will automatically sequence (no requirement to pull the lever, so you can passively deliver via conveyor) and return with some quantity of medicine appropriate to what was requested. That goes into a small inventory on the elevator and stacks with multiple deliveries.
The player would need to go grab the meds from time to time to carry in their inventory, and would need to ingest/inject on the onset of symptoms. Run out, and you slowly rot away until it's game over. :)
Difficulty levels would increase the quantity of items required, or decrease how long the medication lasts (or a combination of).
While this required medication is a bit of a McGuffin, the impending toxic death does serve to add a time challenge and one more thing for the player to have to juggle along with expansion and exploration. By randomizing the demanded item(s), the player is forced to reorient their production to deliver the needed supply (or craft it manually), thus adding the need for nimbleness of design. Imagine having a well-oiled production line, and suddenly you need to divert a portion of it because your medication is being held hostage in exchange for 1000 circuit boards, and 20000 lumps of coal.
This challenge also shouldn't interfere with any other endgame that may be planned.
Another thing I like about this idea is that it wouldn't require a significant amount of new assets. a 3D model for the medication (which could be a re-colorization of the health injector), a 2D inventory icon (same), and a redesign of the space-elevator interface to show the demanded tribute items, as well as the space for medication pick-up. That would make it relatively easy to implement aside from the programming.
I would not suggest this as a default mode of the game, just a variation that the player can invoke at creation to add a bit of personal challenge.