The Greek government should create a second currency
The Greek government should create a second currency to be named the Drachma. The Drachma would be legal tender with the same value as the Euro, but for domestic payments only. Any payment, in the private sector, or to the government, for example for taxes or fees, could be made equally in Euros, Drachmas, or any combination of the two.
The government would start to make all payments, for wages, transfers, etc. with a combination of the two currencies. For example, they could set a ratio of 80% Euro, 20% Drachma. Without any further aid from the EU, the Greek government could increase its spending in this example by 20%.
The government should mandate banks to open a Drachma account parallel to every Euro account so that the Drachma could be freely used in payments through the banking system. There would however be no obligation for a bank to exchange Drachmas for Euros. Also, banks would be prohibited from making loans in Drachma, so that there would be no additional instability introduced because of possibly nonperforming Drachma loans. Each Drachma would again be spent by its recipient, creating a multiplier effect until finally returned to the government in the form of taxes or fees.
Under my proposal, the Greek government could quickly and very substantially increase domestic demand, which was its principal campaign promise and it could do so without the need for agreement on the part of some external authority.
I can see further long term benefits from such a system, not only for Greece, but for all countries of the Euro zone. The introduction of the Euro was a mistake, but abandoning it now would be very costly both in real and psychological terms. Under my proposal, the Euro could be maintained, while giving to the individual countries the possibility of a flexible anticyclical fiscal policy, a possibility that they now lack.