Wow. Fantastic mod - I have been wanting something like this since my first campaign in Rome 2!
As an Athens fan I have some suggestions based on my understanding of where they attempted to control in the pelopponesian war and even into the hellenistic era.
Athens' population could not be supported by only the grain supply in attica and even within the delian league territories at their height- To maintain it, it was essential to import grain via the black sea and particularly from the Bosporus. Control of this was so vital that despite fighting through rebellions of most of the delian league (with some success) for the last decade of the Peloponnesian war, Athens defeat followed very quickly after losing control of the Hellespont and thus access to the Black Sea grain supply. I think this could be reflected to an extent in all the types of victories ( probably by controlling bithinya et pontus, since Nicomedia controls the Hellespont ingame), with at least one (Economic Victory? replacing narbonesis and sikelea -assuming its possible with resource limitations) requiring not only Bithinya but also the Bosporus and Thrace, to really dominate black sea access.
Sicily was an alternative grain supply, and the disastrous sicilian expedition was Athens' attempt to not be so reliant upon controlling access to the Black Sea (along with naked imperial ambition whipped up by demagogues). despite this Athens had few close cultural and economic ties to sicily and Magna Graecia, since ionians had focused colonization on the coast of asia minor and the black sea more than italy. So I think it makes sense that Sicily is included in the set of VC that doesn't require dominance of the black sea trade routes, with italia there mostly for controlling access to Sicily. I reckon it makes sense that military victory requires control of both the Bosporus and Sicily, being the most expansionist.
Macedon itself was probably the greatest and most consistent enemy of Athens after Spartan hegemony crumbled, and eastern/coastal Macedonia had been key possessions of Athens that weren't fully lost until Philip II. The forests and mines were particularly important for maintaining Athens' fleet, and Athens led multiple revolts against Macedon in the Hellenistic period such as the Lamian war. So I reckon Macedonia could fit not only be in the Military victory but also Cultural victory (replacing Libya? to my knowledge Athens had no special ties there, with Cyrene being a dorian colony).
If those are all too close together to be challenging enough, the province with Cyprus in it ( I think Judea?) might be a way of increasing challenge by forcing some kind of foray into successor heartlands. Though the Ptolemies were the main hellenistic influence in cyprus, Athens had close cultural/economic ties during the persian wars and classical era, and reviving this could be a conceivable stretch goal for an Athens that had already dominated the Aegean.
to summarize, I suggest replacing Narbonensis and Sikelea in Economic victory with Bithinya et Pontus and Thrace, and replacing Libya with Macedonia for cultural victory. Cyprus(Judea) could be a fitting additional challenge somewhere, maybe for military victory
Keep up the great work!