Is there any way Greece could default within the eurozone - and then they can keep up the idea that the euro is an irrevocable currency, to stop an inevitable unravelling if Greece defaults and leaves (followed by Portugal and Ireland)?
Or...would this just mean despite defaulting they couldn't return to prosperity, due to the lack of means to devalue?
There's two sorts of problems with the idea of default within the euro.
1) legal. The starting point has to be that the treaties governing the euro are of a complexity where even the lawyers don't understand what they mean. But many (most?) think that a country that defualts EITHER must leave in order to default OR is instantly expelled. The Troika seem to think this, hence their determination to get a 70% default termed a voluntary credit event. I don't think a 100% default for 100% of creditors - what we are now looking at - could be termed a voluntary credit event - but Brussels-speak is a truly remarkable language.
2) practical. Every year Greece spends 10% or so more than it collects, and that is ignoring the debts. So even with the debts written off Greece is going to be running up new debts very quickly. The solution within the euro is all the austerity promised must be delivered, then more because the economy will contract (it is contracting by around 7%pa). I suppose it would be possible to legislate for higher taxes and further cut expenditure, but to work strikes would have to be made illegal. It would be a Soviet style economy with authoritarian control.
I'm with Nigbo - they have to leave the euro. They should have done it two years ago on their own terms. I think we have to accept that Greece will need an aid programme, presumably through the UN, and there are both ethical and legal issues about who should pay. Personally I see all EZ nations as morally complicit in turning a blind eye to Greece's fabricated accounts, so my own view is that Germany should lead the donations. I hope the UK will be generous.