What if, in order for tiers to be unlocked and remain unlocked, the space elevator would require a continuous flow of parts? There would be a minimum parts per minute requirement proportional to current tier unlocks. Possibly with no upper limit, allowing the elevator to eat anything we have in excess. Which may or may not grant additional bonuses(i know this last bit has been suggested before). The way I imagine it, in order to have tier 5 and 6 unlocked, the parts per minute requirement for tier 3 and 4 must also be met. If either of those stop, access to relevant tier and all those above would be locked. This means as we reach highers tiers, the flow of parts to the elevator will be ever growing. But as resource nodes are infinite, this is no issue. This also means if we screw up and remove a couple of factories with no redundancy, we may have to go back a tier or two until it can be rebuilt.
This would accomplish a couple of things:
-Give the elevator conveyor inputs a purpose
-Give the elevator more of a purpose and central role.
-Keeps factories running. I always find it really anticlimactic when containers fill up and everything stops. Stuff would not be wasted, it would go to space and be part of project assembly(whatever that is ;)
-Make power outages hell of a lot more impactful =)
-Extend the game(i get that currently for testing purposes faster progress might be good)
As for loss of tier access to make sense, I'm sure we have all seen seen example of corporate greed ;) Seems to fit the vibe of Ficsit corp nicely in my opinion.