First strike is a bad idea. In Russia and likely China, generals have ability to launch the nukes. They are on bases, in bunkers or middle of nowhere, and impossible to hit without missile. They will launch missiles once see that capital is destroyed. For US, we rely on President but there always Cabinet member that will survive.

Also, all the nations have plenty of SLBMs to retaliate after first strike. Pre-deployed nuke might have made sense back when everybody used bombers and first strike was possible. If so, they would have needed multiple of them, more than could disappear. But it would have been even worse idea, leading to WW3. Plus, back then there was no arms control and need to hide bombs.

For containers, I was not talking about deploying them but using them as retaliation. Could detonate them on the ship or launch short-range missiles from the ship.