My understanding is that the fabrication of the dies are exactly the same, the actual silicon. It's usually the encapsulation, enclosure and testing that's dif

My understanding is that the fabrication of the dies are exactly the same, the actual silicon. It's usually the encapsulation, enclosure and testing that's different. Those are really not big deals, it's not trivial, and they can't be interchanged with consumer product, but it's not as if you are making a fundamental different thing. There are many mil spec fpgas available