I mean, Armenian culture persisted through 100s of years of Persian control, followed by Roman control, followed by Turkish/Ottoman control. So there is no real precedence for one culture to annihilate another. And in our post-modern society, governments bend over backwards catering to sub and foreign cultures versus maintaining and spreading their own.
I think it best just to leave towns as their initial culture as a default, and if people want to mess with it, that’s what mods are for
You are right but we also have a lot of cultures that dissapeared. Picts, Celts, Germanic, Sarmatian etc. (Even if You say that some of them are foundation to other cultures they are not the same and were influenced)
And even Armenian culture changed by others influence and it's not the same as it was before they were occupied.
What I mean about the game is that after some time of holding a settlement You should get recruits trained by the way of your culture and culture debuff for loyalty should dissapear.