So, basically 'Remove Euro!, reinstate Drachma!'?
More or less, from the perspective of the EU as a whole, anyway. To expand a bit, I'd say that the "ideal" EU would be a free trade, free travel/immigration compact, with
maybe an optional currency to go with it to counterbalance the US Dollar. You can have extremely low taxes and a small welfare state like Liechtenstein, or you can have a large welfare state and high taxes like Denmark, so long as you have a more or less democratic form of government and keep your borders open. Such a system wouldn't be beneficial to every EU member, but it would promote peace and economic development in the long run, which was what the EEC and ECSC were founded for anyway.
For the Greeks, they're pretty screwed regardless of what they do, but they'd frankly not lose much from leaving the Euro anyway. No solution is going to be quick and easy, but the best solution in the long run would require the complete restructuring of their economy. In short, they'd probably need to default (which is likely to happen regardless of what they do), cut public spending drastically, cut taxes significantly too, privatize everything that realistically can be, preferably in an equitable, non-corrupt way that gives assets to the Greek citizens that paid for them as opposed to foreign multinationals (as in, through vouchers as opposed to sales). This wouldn't generate any revenue in the short run for foreign creditors, hence why a default would be necessary, and it wouldn't improve the state of Greek citizens in the short run either. In the long run, though, it would allow the Greek economy to diversify and grow, which would solve the overall issue entirely. Of course, such a solution is completely impossible since the foreign banks would lose their investments and the Greeks would lose their welfare system and a lot of their wealth, but there is no such thing as an easy fix.