Very true, and the PAE enhancements of the vassal system go surprisingly well with what Thucydides reports.In a lot of ways, the vassal system will work better for the Delian league than Civ 5's city states. Civ 5 city state alliances were based on how much they "liked" you, whereas vassalage permits forced allies that don't necessary like you, have the possibility of "revolting", etc.
We Mac users would be happier however, if you did it in the 18-civs confinements, because the 40-civs-DLL is, sadly, not Mac compatible. Last year I created a wine version of Civ BTS and tested it successfully, but I deleted it later, since it was pushing my computer too far to the limits, and I'm using the same machine for work, as well. It might appear silly to you, that I argue as a single person but if you take a look, how few people have come here recently compared to, say, 2010, one has to admit, the audience for Civ IV mods is in the decline, and the audience for a beautiful, no nonsense historical scenario even more so. In other words, I would really be p*****, if I missed your Peloponnesian scenario because of that damn 18-civs limitationThe 18 civ limit would be a bit tight, since most cities will be their own civ, but 30 with that dll should be do-able.

Donald Kagan is certainly the most referential figure. But four volumes, are you kiddingBTW, Keinpferd, if you're really interested in the Peloponnesian War, Donald Kagan has an incredible 4 volume work on it--he's a military historian and a good writer, I really enjoyed it. Also, there's an edition of Thucydides called The Landmark Thucydides that is the original work but with detailed maps of the action every few pages, notes in the margins, etc.

I looked at John's map. It's not bad, but I'd make a lot of changes if I used it as a starting point. I'm really more interested in geo-political and strategic than geographic accuracy

Military failures already do go into the calculation of vassal revolt. Pie can tell you all details about it.And it sounds like I'll need to do some work on the vassal system to make revolting a little easier for them[ ]
Our event man is Thorgal, who rather seldomly shows up on these forums, but if you need his support or advice, we can bring him here easily. And he speeks English very well, so no communication barriers here

Excited about your project!