I know that GSG are made on a lot of simplification but it would be very wrong to model the Greek colonisation of the Mediterannean like in EU IV with the Americas.
The period in general would be quite hard to work with since in much of Europe you don't have large states ; I remember there was a small island in the Kyklades which had 4 different cities as an extreme exemple.
It would need another model, very different from the war focus of EU IV to make it work with some degree of historicity but it would be interesting to see a studio try it