Obligatory background reading:
http://hellenicresearchcenter.org/w...6/10/The-Fate-of-Greek-Majority-Psomiades.pdf
One the one hand the situation for Greece looked especially grim, and their French "allies" were deliberately sabotaging them on many levels. However, I can't help but wonder that the Greek leadership at the time basically lost it's nerve, and contrary to their initial desire to defend Eastern Thrace, acceded to the demands, all in exchange for "future diplomatic support" and help with caring for half a million refugees who had arrived in Greece
Let's say they don't.
A week later, the Greeks were expecting to be able to field 60k men in Eastern Thrace:
What needs to be considered is that the entire combat-capable navy available to Ataturk at the time consisted of two old gunboats in the Black Sea. Furthermore, any efforts to organize an opposed crossing would take time, possibly weeks. Lastly, and this is the critical bit,
Greece had a sizeable navy more than capable of stopping any and all Turkish attempts to cross the Straits into Europe via rowboats.
So, POD is that Venizelos is never retained for his services and/or the new Greek Government becomes aware of just how much the French are out to screw them, and they resolve to reinforce Thrace and otherwise stall for time.
Mudanya happens, the Greeks refuse to sign as OTL, demand a conference where they too can participate, one thing leads to another and the Turks start firing on British positions, Lloyd George's government falls, Allied troops start withdrawing and Greek troops occupy Constantinople, the Gallipoli peninsula and the rest of Eastern Thrace - there are some tense stand-offs with local French troops, but at the end of the day the French public opinion is no more inclined to go to war with Greece than the British public opinion is to go to war with Turkey. Riots break out in Constantinople, which the Greek soldiers eventually contain. Ataturks' attempts to cross the Bosphorus and Dardanelles are foiled by the Greek Navy, and the Sea of Marmara becomes a low-key war zone.
What next?
Do we get "a new Balkan War" as the author I linked to above speculates? If so, between whom?
What becomes of Mustafa Kemal, now that he was won everything but the one thing that really mattered - the capital of Constantinople ?