So basically what I'm suggesting is an enhancement to the Custom Civ creation/Edit process. Add a new dropdown, probably to the Abilities tab, that would let you pick the Civilization Factions (limit 3) using a dropdown like Civ Traits.
I originally asked this question on the Q&A in May 2022 and a Dev responded that they would look into adding this feature.
https://forums.galciv4.com/512144/get;3850644
