With a POD occurring anytime after 1600, have the country that we now know as Greece, be unified de jure under the name Sparta, or some variation of it (Kingdom of Sparta / Empire of Sparta / etc)
The Spartan military tradition, or some contemporary form of it must also be realistically revived and imbeded in this ATL country as well.
The Area around Sparta is granted independence, and becomes the city-state of Sparta. Ottoman Turkey (or Greece) then grants land concessions to it, only for Sparta to capture all of Greece. People soon realize that a modern Sparta is NOT a good thing, since Sparta was Ancient Greece's equivalent of North Korea, and an Anglo-French coalition is sent to overthrow the Spartans and restore freedom to Greece.
BEFORE 1600:
Achaemenid Persia allies with Sparta, seeing it as the rival to Athens, and because Athens burned down the Persian city of Sardis (IOTL, burning down Sardis was the Achaemenid equivalent of 9/11, and the Athenian Government was Persia's equivalent to Bin Laden). Persia asks if Sparta wants to conquer all of Greece, on the one condition that Sparta becomes a military and economic ally of Persia- Sparta says yes. A joint coalition of Spartan and Persian troops, led by Datis, conquers Greece in the name of Sparta. Some time later, the Spartan hegemony over Greece collapses (because Sparta was to Greece what North Korea is to OTL's 21st century), and several city-states, including Thebes, Corinth, and Athens, vie for power. It is ultimately the Kingdom of Macedonia that rises to power, and Alexander's conquests of Greece, Sparta, and Persia put an end to the whole bloody affair.