If this really came to a point where the military was “stuck” (which I doubt), I’m sure that Sony would provide a special version of firmware for them, under an NDA. I’d hate to venture a guess as to the dollars of Sony products the military buys. Letting such a special version “out in the wild” wouldn’t be much of a concern, because as I recall, software piracy in the military might not just get someone fired, it might put them in Leavenworth. Still, Sony wasn’t terribly enthused about non-gaming usage of the product because they were and are probably selling them at a small loss and then making it up in game licensing fees.
I agree that if they really had a need for an earlier version of the firmware, Sony would provide one for them.