A first strike that takes 24 hours to get ready? Not exactly a surprise attack, is it? And even if it's as effective as you claim (I doubt it, but who knows...), the counterstrike will still launch and take them back not to the Stone Age, but to times when the Earth's surface was not solid yet.
That's not even considering that them being compliant with the nuclear agreement, they're still a long time away from getting a nuke working, even more from testing it, which would be noticed.
So, not a realistic scenario at all as long as they're not completely desperate with imminent death looming
Biting the hand that feeds IT
