Hi Robin,
I very much sympathize with the analysis of the problem, and your frustration.
The EU is a coordination platform/club trying to deliver public goods, like defence, sanctions, long term monetary and financial stability. But the rules and free riding allow countries to pursue their own interests.
My read of your proposed solution is a sort of hegemonic leadership by Germany. I am doubtful if it could achieve that in one go. The nuclear option of threats might not look credible while risking trashing markets. Maybe a two speed leadership group would be a way forward?
Unpalatable as I know you’ll find it, IR theory talks about side payments. Greece doesn’t back the maritime sanctions because it would suffer a big share of the losses. So compensate it - cohesion payments, maritime investment, naval contracts, immigration help etc.
If nothing changes, nothing will change. Institutional change will take time, so we have to work around it
Longer term, the institutional structure must change. Political and fiscal union. -is it achievable? Otherwise, bits will fall off.