I know that a deterrant that bases on MAD is meant to not be used preemptively by both - or any - side. These weapons are no military weapons. Their use against somebody who owns them himself, triggers your own destruction. That is the meaning, the essence and core of the MAD doctrine.
And there you have it.
No military weapons. It is unreasonable to dream of an "in case of" scenario where these unusable weapons get used in a major exchange and so one must be prepared for it to survive. There is no preparation for assured mutual destruction, MAD. There is no survival worth to be witnessed.
"The only winning move is not to play."
You could as well argue that one needs to prepare to win one's own defeat, or to survive one's own suicide. And that is why all that nonsense about precious staff and perosnell and oublic shelters, is meaningless, and feeds dangeorus illusions. You fall for this illusion yourself: that a nuclear war with a nuclear armed opponent could be "won".
Or would even be worth to be survived.
This folly was fed by both the US and the USSR during the 50s and 60s ("duck and cover!"
), but already during the 70s at least in the West we started to understand that this was totally misled reasoning. Reagan again started to dream of winnable nuclear wars, but he already had to meet a strong civil movement countering him, and I do not mean the peace movement that was massively infiltrated and controlled by the USSR.
You cannot win nuclear allout exchanges, ikalugin. And even wanting to survive them is not worth it, but means despair and horror. Believe it, its better for you. In hell, the living would envy the dead.