I get it that China was far more culturally unified that India or Europe back then, but it was not this level of unified (just about any medium sized European country of that time has 2 cultures minimum), and that definitely did not extend all the way to Korea, and Japan.

Current Han/Cantonese should be one group without anything else - and divided into 5-10 different cultures, whichever way it makes most sense.

This proposal is meant to give all heavily populated parts of the Old World similar granularity.

India, Persia, and South-East Asia have very sensible granularity, and I'm extremely happy with it.

Here's just one sensible proposal of globally meaningful, but you can pick up any scale and stick to it: There are two huge problems: 4 ridiculously large mega-culture-groups, and extreme proliferation of cultures in Europe. There's no sensible interpretation under which it makes sense to put all of Africa or all of East Asia or everything from Crimea all the way to Kamchatka into a single group, but then make a ridiculous number of tiny groups for just about each European country. Seriously EU4, pick one resolution and stick with it.

Just slightly blobby France can have 6 completely distinct culture groups (French, Iberian, Italian, German, Celtic, and Basque), but you can own all of Africa, half of Asia, and a pretty big chunk of Europe and fit all that in just 4 (African, Turko-Semitic, Altaic, and East Asian)? We need a serious talk because EU4 culture and culture group system is just awful. Update a year later - most of these issues got fixed.

Eu4 cultures by development