I have done this without any problems.

If I want to make the Greeks to have one city (at the start of the game), I go to descr_strat and move the unwanted cities to the rebels.
I am still having problems with editing export_descr_unit. When I start a new game, they weren't there.

I want to give the Greek Cities the Carthaginian Elephant Forest, Carthaginian Elephant African, Carthaginian Elephant Cataphract, East Heavy Cataphract and Greek Argyraspid (Legionary).