I think a logical break point would be the Bosphorus and Dardanelles Strait cut off. However the hostility that would exist in the future would need to have a certain land on the Anatolia side controlled by the Greeks otherwise you will end up with the possibility of Artillery strikes, and shut down of the straights. I think you need for victory you would need some of the following to happen :
1. Venizelos stays in power where by the Allies don't cut support ie: "Noting the King's neutrality during World War I, the Allies warned the Greek government that if he should be returned to the throne they would cut off all financial and military aid to Greece". So eliminate his fall (or he does not do a plebiscite). The results of the pleb. end up with "A month later a plebiscite called for the return of King Constantine. Soon after his return, the King replaced many of the World War I veteran officers and appointed inexperienced monarchist officers to senior positions. The leadership of the campaign was given to
Anastasios Papoulas, while King Constantine himself assumed nominally the overall command. In addition, many of the remaining Venizelist officers resigned, appalled by the regime change. The Greek Army which had secured
Smyrna and the Asia Minor coast was purged of Venizelos's supporters while it marched on Ankara."
2. Have the experiences leaders do the follow up at the
Battle of Afyonkarahisar-Eskişehir (July 1921)
Between 27 June and 20 July 1921, a reinforced Greek army of nine
divisions launched a major offensive, the greatest thus far, against the Turkish troops commanded by
Ismet Inönü on the line of
Afyonkarahisar-
Kütahya-
Eskişehir. The plan of the Greeks was to cut Anatolia in two, as the above towns were on the main rail-lines connecting the hinterland with the coast. Eventually, after breaking the stiff Turkish defences, they occupied these strategically important centres. Instead of pursuing and decisively crippling the nationalists' military capacity, the Greek Army halted. In consequence, and despite their defeat, the Turks managed to avoid encirclement and made a strategic retreat on the east of the
Sakarya River, where they organised their last line of defense.
3. Work out a treaty with Russia to not supply gold and munitions.
4. Support Armenians with supplies to keep the Turks busy in the east.
If you have these completed you could end up with a map such as this