Armor removal and armor screws

[motto]

I understand the issues now with the nuts being captive or inaccessible you only have the head of the screw to work on.
The most effective tool I encountered for undoing screws on aircraft (sometimes by the hundred) was a rivet gun with tip adaptor and handle. The principle was that the shock load was applied completely independent of any radial force unlike an impact driver. Of course the screws in that case were 3/16" or 1/4" diameter.
To translate the principle to what you are attempting would require a jack-hammer or pavement breaker fitted with an appropriate tip and a handle to apply rotational force to it.
Maybe just fantasy but who knows what people have laying about the place.

David