For a given currency such as the Euro, either there is 1:1 parity between M0 (central bank money) and M1 (commercial bank money) or there isn’t. Actualy many problems would be mitigated if there was no guaranteed parity, i.e. if bank deposits could fall in value when monetary-financial bubbles burst. If in 2008 there had been a haircut on all bank deposits to write off bad debts, that would have been much preferable to austerity as a means of rebalancing. At least it would be so in substance – selling it to the public would have been a challenge.
However, parity or not parity has to be uniform across a currency. If Euro-denominated bank deposits in some Cypriot banks are overvalued and must be cut then all Euro-denominated deposits in the zone must be cut equally, by a smaller amount. That is necessary for a single currency and banking system to work. Otherwise, Cypriot bank money, or Greek, or whoever’s is next is not actually trading 1:1 with German bank money due to risk perception and we don’t really have a single currency. Or more accurately we have single M0 (central bank money and printed notes) but M1 (bank deposits and nearly all inter-bank payments) is already fragmented and exposed to de-facto exchange rate risk. That risk premium is opaque and thus much higher than if it were a properly floating national currency. Greek businesses, and presumably soon Cypriot ones, are unable to pay for imports with Greek-bank M1 (bank money) at parity. Businesses in countries with stricken bank systems are de-facto thrown out of the single currency already.
The Bundesbank hawks can’t have it both ways. Either the Euro is a single currency, which means a Euro in a bank in Cyprus is a Euro in a bank in Italy is a Euro in a bank in Germany so you can use it for payments, or it isn’t. That absolutely means that whetever happens to one Eurozone commercial bank in terms of crisis response has to be collectivized across the zone. Otherwise we don’t have the benefts of a single currency. We just have the penalties and there is no reason that electorates should accept such a flawed construction.