Already available without perk cost. Alt-F4.
Nailed it.
But seriously, think about other MMO games like Eve Online. The "Titan" class ships are vulnerable but can hugely shift the entire battlefield when deployed properly. If we ever wanted to incorporate the real-world war-winning weapons, we'd need to make it both highly resource intense but also immensely destructive. Pun intended.
Ultimately, I think nuclear weapons bring a whole bunch of ethical concerns tho, and would really upset the gameplay balance.