My hopes would be Boii and Lugii, because some activity is badly needed east of Sweboz. Illegert would add some action between Gaul and Lusota/Carthage, whilst fusing Gallic and Iberian troops without requiring much unique. Bosphoron Kingdom would also add some interest to the north of the Black Sea. I'd prefer something more south-east in the Selucid region, but of all the choices there Atropatene sounds the most promising in that region.
I really dont like the look of any of the others; they're generally adding nothing to already crowded areas. The addition of Pergamon doesnt fill me with confidence on this point unfortunately; nations should only be added if they fill a genuinly useful game niche, not simply because they historically existed.