The problem with casting in stone the Oriental religions is that unlike Europe, religion was much laxer in the Orient. There were forced beliefs and poeple could just mix and match gods or spirits however they choose. Confusicism is concerned more with respect. For instance, it calls children to respect their parents, people to respect their Emperor, and so forth. It doesn't have any churches or priests, but its more like a way of thinking. Confusism is very conservative, and wary of new ideas. Taoism is a little more occult, with a stronger emphisis on gods and spirits. I can't really say about Buddhism, because I don't know very much about it. Most people in China had a Confucist mindset (which made them isolationist, nationalist and strongly convinced of their own superiority even after Chinese power ad waned), and held a varying degree of Taoist and Buddhist beliefs. For these reasons it is diffuclt for us to strictly define which provinces belongs to which religion, unlike the more clear cut lines between Catholism and Protestantism.
Merging Buddhism and Confusism is probably a good idea though. Its difficult to physically distinguish the two anyhow - better to have a single "Oriental" religion, just to reflect its distinctiveness from the other religions of the world. We should take the extra religion slot and use it to distinguish between North American and African "pagan" nations.
As for Chinese "cultures" I'm at a loss for what to do. Ethnically, the Chinese are very unified - you could pull a person off the street from Beijing and another from Guangzhou and they would both tell you that they belong to teh same ethnic group. However, linguistically Chinese dialects are very different. Mandarin sounds to a Cantonese speaker like English to Italian. Its harder to identify now, especially after Mandarin was imposed on the whole nation during the Communist regine, but the Chinese language is slightly different each village over. Over the vast distances, people cannot understand each other (or do so barely). As such, making a single "han" culture is akin to making a "western european " culture that covers everything from Portugal to Poland. However, seperating them into different cultural groups would also be "incorrect", especially the current solution with cantonese and han. The Cantonese are a subgroup of the Han Chinese majority.