What "migrated faction" options are there?

[QuintusSertorius]

Just thinking of local expansion, grabbing Bithynia would not only give you more mines and ports, but some new units. Like Lonchophoroi, who are decent medium cavalry, the Eastern lights and if desired Classical Hoplites - but as you say they latter might be a bit too strange.

You could always roleplay the use of mercenaries alongside your Gallic troops as some ex-mercenary warchief who sees the value in certain Hellenic tactics. Truth be told, only the Thureophoroi are really necessary (good flanker-spearmen which the Gauls don't have an equivalent of), you could make do with Gauls for the rest of the army. You've got FMs for heavy cavalry and Leuce Epos make good support for them.

Hmm, now you've got me thinking about having a go at a Galatian game when my Pergamon one is done. Something about Asia Minor seems to keep attracting me to try migrated factions out there.