Let's see.
You could change the result of the Peloponnesian War, an Athens left in control and with weakened enemies in the early 4th Century might be left in a position to establish a lasting hegemony. This especially requires the butterflying away of the Oligarchic Revolutions that did so much damage. Interestingly, this also butterflies Socrates' trial and execution away.
You could have a Macedonian-controlled successor state set up shop in mainland Hellas; for as long as they retained control of the most major cities it's unlikely it would be easily threatened by the rest. This could then morph into some kind of quasi-Hellenic union.
Post 280 BCE, I think the cause was pretty much lost. In my timeline there is a quasi-independent polity in Greece but this is essentially a vassal state to a larger Empire, and this was with a PoD in 323. If changes are made, they're most likely to need to occur before Phillip II's reign in Macedon.
Alternatively, you could go for the wild card and try to find a way for Greece to develop differently in the post-Mycaenean collapse. The 'polis' as a real political entity only really developed around the 8th Century BC. The only problem is that there are no histories for this time period, so you'd really be trying to make a Cathedral from copying a ruined church with a gutted interior, fallen in roof and graffiti scrawled all over it.