someone had a "Civil war guide", posted on the AARs I thing, but I don't remember exactly.
If some "civilised factions" like Chermonidean Ligue, Epirus, Carthage hold provinces in central Italy I think that they can recruit some citizen troops or samnites, they are recrutable for almost every faction, you can make your civil war as a "Social War" (rebelion of the italian allies) against Rome, after that civil war all italics received roman citizenship.
I wanted to create a civil war in my Pontic Empire but I gave up, so I hope you will succede to recreate a soci civil war, and perhaps make an aar or some screenshots for us