Why not have a Frankish Civilization, as a precursor to the "French". The Franks could have separate UHVs, UBs and UU, akin to how we recycle the Persia -> Iran civilization.
The UHV goals of the Franks would be to create the Carolingian Empire, expand Latin (Roman) Christianity, and (perhaps) keep out Barbarians (Vikings, Magyars, Avars, Muslims etc). The civilization would end with the Germans, Spanish and French spawning. Makes no sense for the Spanish, Germans, French to spawn on the ashes of the Roman Empire, when in reality they were all previously influenced by Carolingians.
The Franks would begin in 481 (reign of Clovis - or we can start earlier).
Doesn't have to be specifically like this, but considering that the Franks laid out the complete civilizational outwork for a good 1000 years (till 1789) and beyond for Europe, seems like they should be shown in some way.
The franks, ostrogoths, visigoths, huns, vandals are already in this mod. They conquer and collapse the western roman empire, and those independent/barbarian cities flip to the new western civilizations.