i think he means that as the banks have proved that they are 100% secure as custodians of your dosh, we can abolish all forms of cash, because your funds are perfectly safe with stalwarts like Lehmann Brothers, whose plastic works at cashpoints even to this day (I think)

If E1 = £1.15 = $1.27 (or whatever todays trading rates are), your electronic fund transfer systems aren't going to care. In todays world you no longer need to carry travellers cheques as your bit of plastic works in whatever currency you're dealing with at that time.

It's not a huge leap from there to suggest that everyone on Greece is issued a plastic card and that they use that for money. OK, so there will obviously be holes in that idea - I can think if half a dozen exceptions offhand - but the potential is there.

Bugger that, it'd mean I'd have to buy my sweeties instead of getting them for free

Find some local magic marker company to supply pens and set the unemployed to work crossing out Euro symbols in favour of something suitably Greek.

I like your idea but it doesn't scale to Italy. If they suddenly switch to the Lira there's no way even 64-bit ATM machines can handle that many zeroes.

That's the easy bit.
You'd still need a currency that was theirs, it was using someone else's that got them into this mess.