Greece should sell some islands to a charter-city consortium.
The islands will remain Greek; the citizens will have Greek passports and will pay a per-capita rate for passport services and military. In return for a pile of money, no Greek laws or taxes apply to the islands.
Likewise, Greece no longer has to pay to support the individual services on the islands. This will help Greece with its current finances by reducing the total cost of services and Greece's public debt by the amount of the sale price.
These islands would make great ports of call for Mediterranean sea-steading. It could be a good baby step towards a couple of ideas that Peter Thiel has been funding recently.