"I suspect the Eurozone will go first, with Greece & the like crashing out"
EU and the Euro could survive Greece crashing out - what they could not probably survive is Italy crashing out - and the new government is working hard to create such conditions. Their motto looks to be Milton's "Better to reign in Hell, than serve in Heaven". The problem is just when you end up being a serf in Hell...
Still Germany and its main allies could "retire" into a smaller "union" with a shared currency. It will be the countries left out that will have to face high inflation, devaluation, and unemployment.
It would be still the most powerful economic block in Europe, and would dictate a lot of its rules anyway. And in many ways, with less ballast on board, they could become even more powerful.
To influence deals, power is needed, and the less power you have, the more you'll have to accept someone else's terms. Countries like China or India will probably dictate their terms...