These are all great ideas, I particularly like how these names have more official historical meanings. I'll add these to the list. :)

adding the H.I.P exclusive cultures would be fun

What about celtiberians?

Italian Albainian = Albanese

Asyro-Persian, because the assyrians were under persian rule for a while; would be neat. maybe asyro-greek as well?

celt+english = brythonic/britons/briton

i dont think i need a source for this, although just welsh=english yeilding brythonic/whatever could also make sense

Any South Slav + Any other different South Slav = Yugoslavian
Slavic + German = Nimietzish (Germanized Nimiecki/Nemec/Nemetsky, the Polish, Czech, and Russian words for German)
Slavic + Hungarian = Ma'dar (Ma'darski, Czech for Hungarian)

Is it possible to change Normans to not include Bretons and instead have Norse-ruled Bretons become Austmen like the other Celts?

I think it would be interesting to have North Germanic + West Slavic, North Germanic + Finno-Ugric, and North Germanic + Baltic. Have the Norse just infect the Baltic.

Not real important but would be pretty neat, Serbian/South slavic-Greek Mix called Sklavenoi, after the serbians that ruled in greece in the charlemagne start

I, for pure satisfaction, I am creating new culture for the group of "classic Latin". For example: Gallo-Roman, Ibero-Roman culture etc.
Adding in step files with dynastic names for those cultures. That is to say, those of the Ibero-Roman culture will have dynasties of Castilian, Basque culture among others.

I think it might be good to see a distinct branch of Norse-Gael culture in Wales. A mix of Welsh and Scandinavian, not just Austmen culture with Irish names. I would call it Kumrig or something like that.

As well as poor Bretons, who for some reason become unrelated Latin Normans. Let them have Bertangian culture, as the result of Norse-Breton relationship.

So I haven't seen any Israelite cultures so I have a few ideas of my own. These are all cultures that still exist but are slowly going extinct. (With the exception of Kuzari, but the Bulanids did take on Hebrew names and I would even change the conditions of it arising is just them being Jewish and being able to adopt the Kuzari culture.)
Ashkenazi+German=Yiddish
Ashkenazi+French=Tsarfati
Ashkenazi+Anglo-Saxon=Anglit
Ashkenazi+Khazar=Kuzari
Sephardic+Levantine=Israeli
Sephardic+Arabic=Mizrahi
Sephardic+Greek=Romios
Sephardic+Italian=Italkim