The northern Europeans must make a stand sooner or later. If they do not stand, then Greece will be back tomorrow with more demands. Standing behind them will be Spain, Italy, and Portugal waiting their turns.
Tell the Greeks a deal is a deal. Take it or leave. If Greek departure will be such a disaster for Greece, then it will be a disaster for all Italy, Spain, and Portugal to see as well.
The European Union and the Euro will be stronger for making the stand.
Another way of saying this is if the European Union is so weak it cannot stand without Greece then it deserves to die.
It would be an inconvenience... but a disaster? Not sure. Do people visit Greece as part of pan-Europe vacations, or for its own sake?