Very quickly (probably more later):
you seem to suggest that b) is better than a) because it would be done without a warning.
Well, that is an impossibility unless you suggest moving back to dictatorships. There are constitutionality issues there.

Also, you seem to misunderstand Migeru's an my use of the word "threat". It does not mean you grandstand and threaten. I specifically mentioned that a balanced position was to not make the Euro an absolute decision. At the moment parties in power have it as an absolute yes, whatever the cost, so indeed Germany can feel that there is not threat of breakup.
Simply saying the obvious, that while you would much rather stay in, you'll also take the situation in consideration, creates a threat, but no grandstanding.

It's like in chess - it's for the opponent to realise that there is a threat. You don't play your move stating "I commit to taking on c7 unless you physically restrain me".

Earth provides enough to satisfy every man's need, but not every man's greed. Gandhi