I think a Europe of Regions is exactly where we should be going. The nation state has had its day; nationalism is a deeply divisive ideology, responsible for so much war.
The EU acting as a leveller and lowest common denominator between states weakens the divisions between nation states, deliberately - precisely because of the dangers of nationalism. And with a weakened nation state, regionalism is relatively more important.
As for tax, defence, etc.; IMO these will sooner or later migrate to the EU level. I don't think regionalism is either unexpected or avoidable the way the EU has been going.
The EU acting as a leveller and lowest common denominator between states weakens the divisions between nation states, deliberately - precisely because of the dangers of nationalism. And with a weakened nation state, regionalism is relatively more important.
As for tax, defence, etc.; IMO these will sooner or later migrate to the EU level. I don't think regionalism is either unexpected or avoidable the way the EU has been going.