Then we have nuclear war. Or we let Putin dictate international politics for however long he has left, and tell China/North Korea/every other bad actor that gets nukes for the rest of time that the game is "be serious about launching nukes offensively and you'll get whatever you want". How do you think that'll work long term?

It's that, or Putin at least maintains a shred of rationality. Or his inner circle takes him out before he pushes the button.