If one was departing from an airport with well stocked duty free (Kefalonia is unlikely to count) one could try to bring a bottle on board and ask the crew to serve it (which hopefully means opening it and leaving it on the table during the flight).

Even if BYO is not quite what one is paying for in CE.

9.5 bottled and 30 people is only 2 glasses each, not overly bibulous.