Some great ideas here, and overall a lot to process, let me try to comment.

The Carolingian Renaissance decision was originally for all Frankish rulers in West Francia, and made them convert to French culture.

In this mod it works exactly the same way with two changes: it now converts Gallo-Roman -> French instead of Frankish -> French, and it does not pay attention to the region anymore, it does not matter anymore whether this is in West Francia or not.

Linguistically, my research has shown this among other things: https://en.wikipedia.org/wiki/Merovingian_dynasty#Language stating "The absence of Frankish literature sources suggests that the Frankish language was forgotten rather rapidly after the early stage of the dynasty."

Right now i actually prefer David the Duke of Knee's suggestion, to remove Gallo-Roman culture altogether and just make them French from the beginning, this would be historically most accurate, as by 769 both the people and the rulers (provinces and rulers in ck2 terms) spoke colloquial Latin as their main language, and only some historians argue that some of these French rulers still knew a germanic language as a second language.

Thanks for the compliment on my modding skills and historical accuracy, i am honored that you ask me to do all these cultural mods.

The levant is an area of my particular interest, i already wrote an alt-history mod that un-arabizes the levant and replaces it with other cultures, that are both more and less historical, depending on the point of view. I agree that a proper historical mod should be, Bedouin rulers ruling over non-arabic provinces, and both rulers and provinces should turn into a unified Arabic culture over time. The big question here will be, what other cultures to use? Some Lebanese argue to this day, that they are arabized Phoenicians. What were the people of the Carthago/Tunisia region before becoming Arab, were they Berber or Punic or Phoenician? What about the Judean / Palestinian region, we have huge issues to this day there and cannot come up with an idea which culture belongs where, and in the games timeframe this was no different, there were Jews Nabateans Greeks Armenians Druze etc etc living there. I am already afraid of even starting that mod, it will be very interesting :)

Berber should probably be its own culture group, with several cultures in it, instead of one unified Berber culture being part of the arabic group.

Areas like southern France, the Iberian peninsula, i sadly do not know all that much about and would have to do a lot of research. I have released 4 new CK2 mods just recently, they are all in a kind of working but not really finished and not really polished state. I would like to polish them a bit more first before starting new mods, i want quality over quantity and i am not happy with the current quality yet but im sure that with enough bug reports and suggestions these new mods will get an acceptable quality within the next couple weeks, and then i can start looking into new mods.

After playing this for a while, i'd suggest Another thing you could do would be to Tweak a bit with the Names of The Component Kingdoms of the francian and german empires, first of all, my comment is purely and solely from the viewpoint of flavour, and i'm completly disregarding historical considerations in my list:

First: Not really a suggestion, just to comment on how both empires have exactly 5 dejure kingdoms, don't know if it's intentional but i love it!

Second: This is just pointing out a simple misstep, that the "Traditional Capital" (aka the one you can move your court to regardless of cooldown if you hold the main title) of middle francia is still luxembourg, as in vanilla, and now that county is outside of the dejure span of middle francia, i'd suggest changing the traditional capital to verdun, as it's not that far away and it's also historically relevant (in game you could view the treaty of verdun as fusing middle and low francia into lotharingia, in a way)

Third: it's a bit offputting to see the two carls holding west and middle francia, as those were divisions made in Karl's will, Pepin's will left his sons with territories named after presedent Frankish kingdoms, Neustria (to Karl) and Austrasia (to Carloman) though they don't necessarily overlap with their merovingian counterparts, they were certainly not named "West&Middle Francia) and with further outlining how you divided up the germans you could rename east francia to "swabia" or "alemannia" they could get their proper names back after a coronation of an emperor of the franks (either francia or HRE) (Plus, i sually rename "Normandy" whatever duchy the norse land in first, "Vanilla" Normandy should be called neustria in the first start date)

Great input,

1 - purely coincidential, i didnt even notice that both have 5 kingdoms :)

2 - obvious bug, i will fix this, shouldnt take too long

3 - this is more complicated:
we have culture-specific names, and we have name changes by event as in the case with Avaria-Hungary or Lombardy-Italy. i think i will need to do the event-based thing for Neustria and Austrasia, have them start under these names and rename to West / Middle Francia later on per event.
East Francia - this looks somewhat legit, according to https://en.wikipedia.org/wiki/East_Francia, it does not exist in the 769 bookmark but exists in the 867 start, as East Francia, which also looks legit. Maybe "Kingdom of the East Franks" would be a good alternative? Alemannia and Swabia cannot be kingdoms, they had struggles with staying a duchy even, the karolingians revoked the duchy status of Alemannia https://en.wikipedia.org/wiki/Council_of_Cannstatt as they constantly tried to secede.
Neustria and Austrasia - i think Neustria is the perfect name for the kingdom of West Francia, according to this map: https://en.wikipedia.org/wiki/Austrasia#/media/File:Frankish_Empire_481_to_814-en.svg
As for Austrasia, the original Austrasia is mostly under Carl's control, while Carloman rules over Burgundy mostly.

Anyways i now have a couple things i want to change, i will do these changes first and we can go from there.

One thing we should keep in mind - the game is limited, some things that happened in reality, are simply not possible in CK2. The reason for the 100 year war is impossible to represent in the game, the king of england cannot be the vassal of the king of france.