Settle down people, the expert is here
I was reading some stuff in the main CK2 forum and it gave me an idea:
Restoration of Jewish Culture
If say, A Khazar ruler restored the kingdom of Israel; Wouldn't he want to unify the returning Jews with a unified culture in addition to religion?
Gameplay wise, I would add a descion that would change the culture of the current Ruler and his most loyal vassals to a new "Israelite" culture. This new culture would use Hebew Localization ofcourse. If possible, could different cultures convert into different versions of this new culture? for example, The Khazars would bring horse archers to the table.
Perhaps a different way, Just one descision that converts to an Israelite culture that has bits and pieces from the returning jewish cultures? This would reflect the different cultures adding their stuff to the table, as it were.
Did Germans try to restore Roman culture after forming HRE (thus restoring the Western Roman Empire).
Did the Turks try to turn Greek after conquering Byzantinium?
Did ERE try to stay Latin?
This really should not happen. It might happen in EU4 and definitely could in Vic2, but in Medieval Era? Nope.
I actually agree more with Nyrael with this one. A sort of Hebrew language restoration is highly unlikely in this time period - it was only really possible in the 18th and 19th century due to higher rates of literacy, fast communication, and the rise of nationalism (which manifested in the Euro-American Jewish community as Zionism). It is more likely, as Nyrael said, that if a Khazar somehow reformed Israel that either Israel would be Khazarized or the Khazars would adopt the culture of the majority Jews there (likely the Levantine Mizrahi Jews). Even if the Kohen Gadol attempted to restore the use of Hebrew, for instance, I would think it would be in limited religious and social contexts, similar to Latin in Catholic Europe or classical Arabic in the Muslim world. I personally think there is nothing to suggest that Hebrew would have to be a uniting language - it could easily be Sephardi if the upper class is dominated by Sephardic Jews, for instance, or German if its Ashkenazi Jews.
That said, I can see the possibility of a melting pot that represents the various Jews making aliyah coming together and... well, blending or what have you, though it would in any case be an extreme abstraction. I'm still not too fond of the idea, though (especially given how messy melting pots can be), but I can throw it in if enough people demand it (and/or if OrdepNM demands it).
What we're talking here is the "Sabra" culture which is currently taking over in Israel. These are jews who were born in Israel (like me) and are no longer immersed in their parent's old cultural traditions. It's quite clear things like Ashkenazi and Sephardi are on their last legs around here as most of the aliyah people grows old while the more recent newcomers Beta Israel are still strong, but the younger people would already be described as Sabra as they lose touch with ethiopia. If it isnt already, Sabra will eventually become the dominant jewish culture in Israel.
Now, like Nyrael said, restoring hebrew as a spoken language in this time period is tricky, too much illiteracy. Maybe it would be introduced into the royal court for written documents only and it would slowly trickle down from the elites to the plebes over a long stretch of time, but thats a big maybe. On the other hand, culture isn't just about a spoken language. Regardless of language, kaifeng jews are gonna start losing touch with chinese costumes over time, and assimilate into, welll... Sabra, so there is something to be said about nsinger's suggestion.
Now as for gameplay, Im not sure I'd want this. While it would be good that jewish rulers wouldn't have the foreigner relations penalty for other jewish cultures (which is not very accurate for jews), it would utterly suck if all sabra courtiers would spam using one and only one portrait set and eventually all but say, the caucasoid Ashkenazi, would exist in Israel. Also this stifles the possibility of several fun flavor events for jews of different cultures interacting with each other, stuff like "some of the new arrivals at your court come from far away Yemen and claim they speak hebrew, but none of us cultured in hebrew can understand what they say. And argument has erupted in your court over who speaks proper hebrew!"; Kaifeng and Bene Israel clash over who has the best asian cuisine! etc.
A better method IMO would be to have it done by trait and event. After some time, the king of Israel gets an event titled "embrace the Sabra culture". If he decides to do so (and he should), he gets a Sabra trait that nullifies the foreigner malus from having a different culture within the israelite group. The trait would be inherited so all sons of Sabras would be Sabras and sabras could convince other non-sabras to stop being bigoted and get the Sabra trait. Like this you also avoid another melting pot (which are messy by definition).
Now, how many times did I say Sabra through this entire post?