I mean, borders are a bit complicated

Point remains that we have a general assimilation of more and more provincial elites until we have Roman citizenship apply to a wide breadth of people.

At the same time the title emperor to the Roman was never the same exclusive title it became in the Middle Ages and later so someone holding a title of imperium did not mean it needed to be someone from a specific bloodline. They always saw it in a more complex political organization, that is why we have emperors seemingly splitting the empire. To them this was obviously an office of high prestige, but it was an office with administrative and military power, not some blood right. And they never saw this as breaking the Roman Empire apart, but making administration or military organization easier.