Swabian (just like Saxon) can be recognised by dialect, if heard in direct contrast to other subcultures. I concede that a Hannovarian can probably not be recognised that easily, but there could/should be a bit more subdivision in Victoria III then just North and South German, just like there should be more subdivision for other countries).
I'm curious as to how the new culture system will work out in the new EUIV DLC where accepted cultures can be promoted/demoted (etc.); under a set of prerequisites, something similar for Vicky II could be used to simulate the promotion of Magyar culture for Austria-Hungary and/or the nationalist movements that eventually split the Ottoman Empire apart.
It could also open up something akin to levels of autonomy/home-rule in colonies/protectorates such as British India or Egypt, where the promotion of a native culture would allow them to become the bureaucrats/aristocrats in those regions.