I think the 8 city elimination is more than fair. Think about it, if 8 cities of any of the Roman halves are taken/destroyed (which is a devastating blow in ancient times) the empire would surely collapse. This is what happened to Rome. They lost too many cities and they just went straight down. The cities in the scenario represent large cities and in ancient times those large cities were the only thing holding the empire together.. the lost of 8 = no more empire.
Keep it to some ammount of cities for elimination, taking it out though will be completely incorrect historically. Atleast 12 cities or less is correct..