Nice research there, ahowl.
I think you could throw in some barbarian population (e.g 10) to represent the less Romanized elements in Latium, like displaced Gauls. But that's up for debate.
As for whether there should be specific Latin units, I think Roma Surrectum (and perhaps Europa Barbarorum?) dealt with this by creating the "extraordinarii" unit type, which can basically represent any of Rome's Italic allies, being recruitable in several regions of Italy. Of course, the extraordinarii were something of an elite unit, so more ordinary units would be lacking.