What would be far enough? If having a new treaty with teeth isn't enough for the bond investors, they must think that there must be a political union of Europe and not just an economic one. Countries would have to be governed from Brussels and not just their economies. Everybody knows that's never happened in all of history in any kind of democratic fashion, the latest attempt being the Third Reich.
So maybe all this does signal an eventual breakup of the EU. Not just Great Britain will be out but everybody.