Would the Greek financial crisis have even happened in the first place? A unified currency zone would have lead to a much more unified European economy, with ease of trade and commerce making it unlikely that any one country's economy would be that much worse than the rest. More likely, Greece would have suffered a significant recession of the sort that's happening in Germany and France, not the much deeper recession it's suffering IOTL, so unemployment and lost tax revenue wouldn't be as pressing.
A unified currency would also have allowed Greece to borrow at much lower rates. IIRC, the immediate trigger to the Greek financial crisis was lenders anticipating the Greek devaluation and demanding much higher interest rates to compensation for currency risks. If Greek debt were denominated in EU Marks rather than Drachmas, they likely could have continued to borrow at reasonable rates, giving them the cushion they'd need to implement a reasonable austerity program to fix their long-term fiscal situation. Also worth noting is that a unified EU currency implies an EU central bank that could serve as a lender-of-last-resort to backstop the Greek government's fiscal situation.