@auhsojsa The Spartans and the Athenians, as well as the combined forces of all the other Greek City-States.. didn’t mean a thing when the Roman empire emerged.
It’s obviously hard to argue what would have happened hundreds years after a historical event, if that event had turned out differently. How would WW2 have played out if the British had won the American Revolution?
But empires come and go, and the Greek Empires saw their end well before the emergence of the Roman Empire. Given the poor management skills the Persian Empire already had, I highly doubt adding more unwilling subjects to the mix would’ve made it any more successful or stable.