Being a back-stop for the national debt is one of the core functions of a central bank. That ECB thinks this function is something that is optional and something it should be applauded for is like having a fire department that first refuses to put out fires, and then expects applause for not intentionally letting anything burn down in years. That is a reason to leave before it gets worse.

As far as reform goes, the structure of the eurogroup meetings (as described by Varoufakis and he has been in the room) is Germany decides. And the structure of the ECB meetings are secret as far as I can tell, but ECB gets their political cover from the eurogroup. So there will be no reform that doesn't fit Germany and Germany will decide if and when there is a reform. Non-germans has no vote on that. And no amount of Italian pressure is likely to create that will in Germany. Nor will threats to leave (sorry melo).

There is no process for exiting the euro but neither is there any process for kicking a country out of the EU. Countries can be fined and lose voting rights when in violation of treaties, but that is rarely applied. The only reason the EU has such power over Italy is the ECB in combination with Italy's current account deficit. If Italy de facto leaves the euro (say capital controls and parallell currency) or even de jure, the ECB stick is already removed (but can and will hit hard on the way out) and the rest is up to politics and the courts. Unless the other EU states follows up ECBs financial blockade that we saw with Greece with physical blockades, of course. Then things would get really interesting.

However, I think this is academic as judging by their deal with Lega, I don't think M5* has the skills or the will to leave the euro.