I was doing some reading about the first balkan war, and one thing I noticed was that before it begun the population of Greece was 2.6 million. In the year 1912.
In this timeline Greece has a population of 2.2 million in 1860. At this rate it will be over 5 million by the time the war kicks off. Additionally Greece was the considered the weakest of the big three balkan states, only raising an army of 125,000. This army did very well for itself, but still doesn't compare it absolute terms to the 250,000 serbs or 600,000 Bulgarians. Greece can probably raise a number of men similar to the first balkan war on its own right now, and it's navy is not behind either.
It's extremely impressive how strong Greece is right now compared to our history. Especially when you consider its economic strength will allow for a better utilization of that larger population.
A further difference is the political parties priorities. The nationalist party, wanting expansion, will probably ensure the army remains large, well funded, and well equipped. The question will be if the leadership and organization is also maintained at a high quality. Though knowing Panos Kolokotronis was in the military after war sets things up for a solid tradition of martial aptitude.
This all means that Greece is in a far better state to take the fight directly to the ottomans. Now, this doesn't mean they could win in a 1 v 1. In the early stages perhaps, but in the long term, as long as one country has more than 5x the population of the other, the smaller will get grinded down. It's possible that the greeks could make a mistake in this area, thinking that if they mobilize to the hilt, and then take a chunk of territory in a blazing campaign of local superiority, the inevitable great power interference will allow them to keep their gains, but I doubt that Britain will look kindly on that sort of blatant expansion, at least once they start trying to prop up the ottomans as a buffer to the Russians.
A wiser move would be to open up a second front in a Russo-Turkish war. This was narrowly avoided in the alt crimean war, to great gains for Greece, but I doubt that it can be avoided a second time. First of all because there's little the ottomans would be willing to give that would satisfy Greece the same way as Epirus and Thessaly. Perhaps Cyprus? But if the British hold that it will be a non-starter. And Salonika is simply a no go. Thus the nationalist greek government would go to war, However with the greater land, population, and wealth Greece will have in, lets say 20 years for an 1880 war like our timeline, it will be able to offer a far more credible second front then they could have offered in the 1850s. 200-250K troops would divert at least an equal number of ottomans, and probably more if they want to have a chance of holding the greeks back. Such a diversion is utterly untenable for the Turks, considering they put around 400k men on the field last time. They'll need at least that many to hold back the Russians, and probably more as the decades roll back.
A complete ottoman collapse in an 1880s war could allow Greece to make spectacular gains, assuming ofc that the other great powers do not interfere too strongly. Many suspicious eyes must be cast on Russia right now, considering their diplomatic blunders in the great eurasian war. And of course if Greece + Russia do break the Turkish back in the 1880s, that would open up a whole new dimension for the timeline. The great enemy would cease to the Ottomans, and instead it would be politics with the other balkan minors, and adventuring as a secondary power, with perhaps an eventual final showdown (perhaps related to a world war) with an eye toward Anatolia.
Basically, I'm just talking about how far Greece got in the 1910s, and considering how much further this Greece could go when it's in a similar position, but in the 1860s.