In order to strengthen the principle of liability at the level of sovereign states, the framework of monetary union needs to be improved. Even with regard to government finances, liability and control must be in equilibrium. In the Maastricht framework, both liability and control were, essentially, located at national level.
During the crisis, however, we moved away from this: control remained national, whereas liability has been increasingly transferred to the European level. While national governments take independent decisions on debt, the community is liable for the consequences. This set-up is a breeding ground for renewed unsound developments. I therefore see only two convincing options.