Falcon900: You fail to realise that, as history shows, plenty of ostensibly 'sane' individuals have pulled some pretty crazy sh*t in situations where there is no perceived gain or advantage. Also, Russia's 'vast' conventional forces are nowhere near as vast they once were. Plus, an entire generation have grown up with the idea of 'democracy'. Doubt they'd go so willingly to their doom for The Rodina as is true of their WWII comrades (would they ever have done, anyway??).
Trident, lest you choose the ICBM route (plenty pitfalls there & not practical for us anyway), remains the only credible option for strategic deterrence. Some lower - level tac options would be nice too, mind.
Nor do 'suitcase' bombs exist - at least not in the way you imagine them to, anyhow. What might be contained within a ships hold, however is another matter entirely.
Oh, and we didn't 'stand back' until the Wermacht had been bled dry, either. I think you'll find we were fighting in North Africa (and elsewhere) whilst building the necessary materiel for an invasion force. Or would you have us mount a 'reverse Sealion' in barges??
Best,
Frank