@Derek Pullem - That I think would probably be a post-provincial reform (in my mind) - after all, simply controlling those regions is a task, but local unity is still important, so even in a Social War analogue, I can expect it to consist like a League-in-Parts (Ionian Circuit, Macedonian Circuit, etc) - but with all the polis also part of Athens proper. This would probably also count for the further afield colonies - essentially local authorities and organisation tied together.
That could be quite a powerful trick though, and start the road to "De-city-state-ification", replacing the City State identification with Circuit. Which would likely change the shape of future settlement for a successful League. The question is whether Athens wins but makes concessions - or loses and despite the window for fragmentation, the League sets up a new headquarters. (In which case, where? We're basically talking about turning a city into a Washington-DC style site.) In theory you could have a defeated Athens essentially rebuilt on that premise. An "Athens as it should have been" if you will.
I do think that it would be quite a successful league though - especially if it does thinks like abolish in-league tariffs on goods or similar practices. That'd cause a economic boom, and all the forces that would otherwise be fighting each other can focus on pacifying the north.
Actually. That is the really bloody obvious option. We already know where a new capital would likely be if the League makes an effort to expand in the Black Sea and unify those Greek Cities.
Byzantion.
Which, considering its location, and the time period - would likely make trade a major focus, much like its hypothetical rival Carthage. The two may be more interested in trade with each other than war - and with an early social war, this "Byzantine League", with its strong trade focus, and relatively large army since it is pre-Alexander could easily take the role of Epirus and then some in Italy - butterflies permitting.
I won't lie, if I knew enough about the time, I'd write a TL. Sadly I'm no
@Sersor .