A Northern EU doesn't solve the problem of German exports. A Commonwealth currency isn't appropriate, for entirely the same reasons the Euro was a big mistake: one monetary policy cannot cover such a diverse range of commerce without very tight political integration.
The reason we blast Brussels, TW, for not asking permission is far beyond a political argument alone. It goes to the heart of the false democracy of the EU. The unelected peers and the referenda used to legitimise it had no integrity and barely give any mandate to govern at all. To transfer/loss of the sovereignty of our nations should require the actual and direct consent of the people, not a slow leaking away of governance based on a 40 year old trade agreement.
The EU has not managed to fulfil any of it's promises or expectations. It is corrupt beyond belief with a vast array of bureaucrats paid well over their due they would expect in individual countries, inefficient and uneconomic to the heart with unaudited accounts and little oversight, a propaganda budget of several hundred million to promote it's own policies, not to mention the constant breaking and ignoring of fiscal rules.
To save it requires an honest inspection of which countries can actually abide by several core principles and then bringing those few (France, Germany Belgium and Netherlands most likely) into close integration.
The rate of change that has been expected is far two great, and to save the eastern part of the EU requires an entirely different arrangement. Possibly over the next few hundred years the areas can merge.