Having Greece out of the Eurozone will be a devastating situation for both Greece and the Eurozone. ONe of the reason why would be a devastating situation for the Eurozone is because the EU banks are exposed to Greece and they would loose a big percentage of value of holdings. Because of that situation, it's a win-win solution for both Greece and the Eurozone to renegotiate Greece bailout in order to allow Greece to stay in the Eurozone and avoid a big catastrophe in the European economy.
Greece has to be able to negotiate its bailout in order for the aid it receives from other countries to have the best possible effect. Greece knows best what it needs, and if other countries want to help, they should listen to what Greece wants. Otherwise, the bailout may result in wasted resources.
Attempts to renegotiate the previous bailout package for Greece should always be an option. If things were going the other way and the Germans and the EU wanted to renegotiate, it would happen for sure. Why shouldn't the Greeks and their elected representatives, whomever they happen to be, be allowed to do the same thing?
On one hand, there is a tendency to want to help out a country in dire need such as Greece, just as charitable institutions seek to help the poor and the destitute within a given society. There comes a point, though, at which to help is actually harmful in the long run. Rather, Greeece should be made to work hard to bring itself up out of ruin.