As Martinghoul wisely points out: You can't have it all. You must choose one or the other, both come with consequences. And Germany cannot do a thing if Greece decides to default. By the way, are you blind? Germany is more than happy to let Greece off the hook, to let Greece default and to let Greece leave the union. Of course Merkel would never openly say so, but this is the overall policy stance towards Greece at this point in time. It was very different 2-3 years ago but Germany is fed up. So, if Germany was the only creditor there would have not been a single additional extension granted last week. Germany would have forced Greece to make up its mind, and it very much would have the right as creditor to demand a decision. But Europe is not just Germany. There are plenty others in the Eurogroup who have a vested interest in being perceived as supportive of Greece. But this seeming support is as self serving as Greece's government, as self serving as Germany. Get real, and look at the facts and stop believing the nonsense you read in some gossip blogs.
No, the reality is that Germany is terrified at the prospect of ANYONE leaving the eurozone. Why? They know anyone leaving means others will follow. If that happens the whole euro project collapses.
In public, they have to show they don't care. In fact, presenting a hardline is the way to go. But internally they know they can't afford to let anyone go.