Will you have the mentioned assets after India's first strike ?A S-400 cannot protect against a sea surface skimming cruise missile in a coastal attack from a submarine, aimed at a high population density port city like Mumbai. Pakistan has SLCMs and modified anti-ship missiles such as Harpoons. Also an S-400 cannot protect against a nuclear artillery shell lobbed at a city close by such as Amritsar which is within shelling range from Wagah.Nuclear booby trapped trucks left behind or driven close to the border or in the path of an advancing army would also not be intercepted by S-400s.
In an all out nuclear war Pakistan would be launching every single one of its assets along with decoys, immediately as there will be no more wars to fight "tomorrow".
The S-400 was designed by Russia for protection over its vast territories where flight times make detection far easier. The other nuclear adversaries are separated by distance and don't share a contiguous border.
India and Pakistan share a border with close proximity of it's population centers. Even the threat to Israel is not that close or severe, since Iran is much further way.
With India, even a "suitcase bomb" could be delivered by suicide squads.
There is a reason why no country likes a nuclear armed neighbor. Tye USA ensured Mexico never acquired nuclear weapons technology even though a Mexico US conflict is remote..
Why do you think India will give pakistan any time to launch these assets ?
Do you have second strike capability that will overwhelm India's Multilayered ballistic missile defence shield of which S400 is just one part.
Idea behind S 400 is just to make you difficult to hit the target thus you will have to deploy more assets for a single target, even then you won't be sure and it is working perfectly.
Between how will pakistan save itself from AGNI ,Brahmos etc ,no one talks about it.... Only then you might get a chance to hit India.