Please tell me you arent considering leaving Syracuse or Pergamon out - their potential was incredible, even if not fully realised.
Illyria and Numidia would be a shame to waste too.

These are all foetal nations that could have become great had they not been snuffed out by Rome. Bottom line is that we'll never know the potential that any of them really had, were Rome never to come to power, so you should base your inclusion on two things enjoyability (we are all here to game after all) and availability of information (for factions with factual depth). That means staying tight to the mediterranean basin for the most part.