If we're looking at changes for ck3 I would definitely like a more robust culture system (celtic>brittonic>welsh rather than celtic>welsh) as it would create a more immersive game for several reasons:
It would allow modders more depth when they create new cultures or want to mod things dependent upon culture (instead of having to mod in if: breton, welsh, pictish they could mod if: brittonic
For theapplication of game rules across cultures (celtic>goidelic could be given access to tanistry succession so that celtic>goidelic>irish and scottish both got it but you're not applying it to celtic>everything)
and for the application of foreigner debuffs/benefits (a breton and a breton could be 0 malus, a breton and a cumbrian could be -5 malus, a breton and a scot -10 and a breton and a swede -20)
I feel that the ck2 culture system is a bit too simplistic
It would allow modders more depth when they create new cultures or want to mod things dependent upon culture (instead of having to mod in if: breton, welsh, pictish they could mod if: brittonic
For theapplication of game rules across cultures (celtic>goidelic could be given access to tanistry succession so that celtic>goidelic>irish and scottish both got it but you're not applying it to celtic>everything)
and for the application of foreigner debuffs/benefits (a breton and a breton could be 0 malus, a breton and a cumbrian could be -5 malus, a breton and a scot -10 and a breton and a swede -20)
I feel that the ck2 culture system is a bit too simplistic