I agree. It is entirely reasonable that it may cost some money to provide for training and/or transportation for the employee to change job roles, get reassigned, or simply go back to "the government" (that's too nebulous; we should just call it the homeworld, which should not be viewed as merely another colony).
But Promethion? That's kind of silly. It's like saying we can't promote you or change you to another job role because we just ran out of staples. Everybody knows that staples are the Promethion of the modern office, right? Umn, wait; don't we mostly write code and didn't we go paperless last quarter? Oh, yeah, it's because we're out of coffee cups in the break room. Don't we encourage employees to bring reusable thermal cups from home? No wait, it's because we have no more supplies to clean the toilets and urinals; yeah, that's it! Housekeeping is using your old ties for that....
Well, I'll probably mod it too, but for now I just did three trades, so I have 78 Promethion and 29 Duranthium, since you need the latter to have starbases upgrade themselves.
Even Duranthium mining starbases require Duranthium to be upgraded. Wait, what now?