Persians need to be in the mod as a major civ. They basically formed the eastern border of Rome's influence, serve as an excellent foil to Greece in the game, had access to perhaps the widest variety of mercenaries and elite corps in history, and contributed a lot to the world in religion and economics.
Also, they're one of the only civs to bridge the entire likely time span of the game. From early Greek written record down to the end of the Roman empire, they were there. In fact, if you're thinking of including the Scythians, they too were an Iranic people and could very well enter the game as a native ally of Susa AND of Ionian Greece.
As for Carthage, the entirety of North Africa will have to be treated somewhat differently for the purposes of the timespan of this game, which I'm assuming stretches from about the Doric conquest to about the fall of the Roman Empire.
In the earliest days, North Africa was 3 parts: Egypt, Egypt's vassal states, and their rancorous neighbors. Then Phoenicians settled North Africa and initially adopted much of the culture of Egypt to the east and the Berbers and Numidians to the west and south. The entire realm of North Africa was then divided into mainly Egyptian influence and mainly Carthaginian influence. Egypt let its military go and focused on the unique economic boon of being trade neighbors with Carthage, but also friendly to Greek and later Roman interests. In this way North Africa was a;lmost entirely Romanized and demilitarized. Carthage could be represented as having a strong early and midgame military, and a good - to - robust economy with many fishing upgrades and warship upgrades later in the game. One of its royal guard units could be a warship. The other could be an elephant unit, which would make up for its relatively weak infantry. (I'd think it would be most fair to make the rest of the cavalry weak instead, but in fact historically North Africa was the horse country of the Roman Empire, and their light cav were exemplary.)
I like to think of the Mediterranean world as a hexagon. In the center of the hexagon you have Greece, Rome, and Etruria; the hexagon can be viewed each of two ways.
If the hexagon is drawn so that it rests on a vertex, the sides are in clockwise order from top right: Germanic peoples to the northeast, Persians and Arab or Syrian groups to the east, Egypt to the southeast, Carthage to the southwest, Iberians to the west, and Celtic tribes to the northwest.
If the hexagon is drawn so that it rests on a flat side, the sides are in clockwise order from the top: Germanic peoples to the north, Persian and Scythian and other Indo-Aryan mounted tribes to the distant northeast; Syrians and Arabs to the southeast; Egyptians to the south; Carthage/Numidia to the southwest, and Celtic tribes to the northwest.
This framework is very simplified but should give you 8 or 9 civs to begin with, and their relations; minor native allies should be drawn from within or between these groups. For instance, between the Germans and Persians you could have the Scythians, Huns, etc, between Arabia and Egypt you could have the kingdom of Judea, between Carthage and Gaul you could have Iberian groups, between Gaul and Germania you could have Thule (which could be early Vikings or even Laplanders or Inuit) etc.
as for Etruscans, I'd like to see someone make them into a major civ, but they are less well-known historically and could probably be set up as a minor ally.
Crunkatog on ESO
Bart331 balance suggestion: aztec: remove civ
Voltiguer: Ender, Sioux in 1.04 will be a top civ, no matter how many layers of Sioux goggles you put on
schildpad on Elephants: ...their mansabdar unit sucks so hard it looks like a black hole
Crunkatog on Steam.