The other day, I posted on that the Athenian occupation of Sicily wouldn't be possible, due to the relatively small numbers of Athenian citizenry, and the exclusionary hereditary nature of Greek polis citizenship. So I was wondering which select Athenian politicians could have instigated internal social reforms that would have led to the civil enfranchisement of Metics and subordinate allied polis's within the league. What series of political processes would be needed to have led to the ultimate amalgamation that would transform the allied city-states into a perpetual federation that could go as far to subjugate the remainder of Hellas, and later assert control of the colonies across the Mediterranean as part of a imperialistic protection racket?
The Delian League started out as an actual league/alliance, and only morphed into an Athenian Empire later on. If you want to keep the League functional, it has to be not a centrally imposed Empire, IMO, unlike what what happened OTL. However, if it stays as a voluntary confederation, I don't see it doing the 'imperialistic protection racket' thing.
If the League managed to transform itself into a 'United States of Greece' (yes, it would only have <1/2 of Greece, but the USA has < 1/2 of 'America'), I think it could have a good future. How this would relate to Sicily, I don't know.
Also, I suspect you need to keep some external threats to keep the League together (? Sparta, then Carthage, then Rome ??), both to keep the minor states in line, and to keep Athens knowing it NEEDS those minor states.
I suspect it's doable. Not quite sure how to.
I think it might well lead to a better, more functional world than ours.
If Magna Graeca joins, that will do interesting things to the evolution of Rome, and Europe...