This looks like a fantastic mod, I can't wait to play it. I feel like I should point something out though - I see it crop up a lot in mods that deal with the post-Western Empire period. Please understand that I'm just trying to be helpful and not trying to be the history hall monitor just because I work in the field.
Technically speaking, by the end of the 5th century (by 500 C.E.), every territory which was ruled by Romans prior to the dissolution of the Western Empire should still be cultured 'Roman.' The only real exception that I think could be argued for would be eastern, lowland Britain, which could probably be identified as something-Germanic by the 500s, and Western, Highland Britain, which should still be considered 'Romano-Briton' culturally. I wouldn't even go so far (at this point) to differentiating between Gallo-Roman, Hispano-Roman, Romano-African, Italo-Roman, Greco-Roman, Romano-Syriac, Romano-Egyptian culture at this point. Certain the Eastern provinces would not lose their unified 'Roman'ness until at the very earliest the Persian conquests of the early-seventh century (600s-630s), when you can start to see Monophysitism emergning in Syria and Egypt as a component of ethnic identity - Coptic and Syrian, respectively. In the West, the de-Romanization of Italy would actually precede that of Gaul or Hispania, due to the ravages of the Gothic War (540s-550s critically) and the successive Lombard invasion (after which you could label Italy 'Romano-Lombard' outside of Roman-held Rome, Ravenna, and other surviving holdouts), but by 600 you can start to see Gallo-Roman (Occitan), Frankish, and Hispano-Roman cultures emerging out of the Western Provinces, and a Romano-African culture (as distinct from the late Roman culture which should still exist in Thrace, Anatolia, and Palestine) beginning to take shape in North Africa. The Balkans, outside of Thrace and Thessaly, you could probably culture as 'Slavic' or 'Romano-Slavic' by 630, although 'Romano-Slavic' isn't really a term we use. 'Roman,' however, should still apply to Thrace, Thessaly, Anatolia, and Palestine until the 650s, after which the Arabs securely held Palestine, and the surviving Roman provinces in the Balkans and Anatolia were converting to the theme system, which technically you should label 'Romanoi', since the medieval Roman Empire we erroneously and anachronistically call 'Byzantium' was never called that by its inhabitants, who always referred to themselves as 'Romans,' --- just in Greek.
I have no idea how a system like this could play out: a series of events, maybe, kicking in when years change, or when a territory has been removed from Roman Imperial control for a certain amount of time? I'd just love to see a mod reflect the current historical thinking on identity in the Late Antique period, and since I haven't got a clue how to do one myself, I thought I'd pop in and see if I could be any help from a scholarly perspective. Sorry if I annoyed anyone.
