The PoD has to be before 1800 or so, I believe, the point being that you need the Ottoman Empire to develop as OTL up to a certain point in order to let the ideas taht gave rise to the modern Greek state germinate, and then you need to fail in 18th century reform endeavours and so go down the tube in the early 19th C as OTL, which allows these intellectual trends to manifest as the Megalist conspiracy.
Although I consider the success of that conspiracy in its original aims (Greek-dominated neo-Byzantine Balkan-Christian state)
supremely unlikely, it might just about be plausible in the event of a wholesale collapse of the Ottoman Empire and Russian intervention on a massive scale. This isn't possible in OTL's circumstances, but with a Napoleonic victory you
might be able to pull it off. We won't go into the consequences, which are very likely the Morea ethnic-cleanings on a massive scale, and eventual national conflict between the Greek elite and their Serbian and Bulgarian vassals.
After that, the issues of comparative sizes, resource-bases etcetera are all in play, and the Greeks did very well to get what they did OTL. They could plausible secure northern Epirus, Cyprus, and much of eastern Thrace on top of that (and Imbros and Tenedos). Istanbul and Anatolia both entail pretty much insurmountable logistical difficulties.
Greece would have gotten that territory if the Treaty of Sèvres (WWI) worked.
Which it wasn't going to. It was based on illusions, the results of negotiations with a government that had lost control of a population and armed force with no intention of surrender.