The aim must be to design the instruments in such a way that they stabilise the euro area without creating wrong incentives. That is the only way to succeed in completing banking union. Do you understand this to include the option of allowing individual countries to go bankrupt?
If we take the no bail-out clause in the European treaties seriously, it must be feasible to restructure government debt in an emergency situation. But that should not be to the detriment of the whole financial system. An orderly restructuring can only be a credible measure if it does not endanger the banking system.