So a "No" in the referendum and a Grexit would probably be the only option. The immediate economic damage would be catastrophic and the EU would probably have to provide emergency aid in the first phase but a reset is needed, both economically, politicaly and diplomatically. That is providing they manage to stay in the EU at the very least. A Greek exit from both the EMU and EU would leave them completely alone and almost rogue, it could be cataclysmic. Just imagine the impact of losing free trade with EU countries, having to renegotiate treaties and attempting to pay for vital imports with a massively weakened Drachma while the loss of freedom of movement risks devastating the tourism industry... it boggles the mind.
It's a tightrope. But no matter what happens Greece can't burn all their bridges with the EU, they will need assistance after the reset.