Having played a bit, I'm pleased to see some of the changes, particularly the first few steps at including a fully fledged Taiping Rebellion.
However I think a few more changes really need to be made, including:
1. Split up the East Asian culture group, with Japanese and Korean in their own individual group, similiar to the setup seen in Magna Mundi for EU3.
2. Make China the Union state for Chinese cultures, tolerating all Chinese (not just Beifaren and Nanfaren).
3. Perhaps make the Chinese Union State a seperate tag from the Qing Dynasty, so that China can properly revolt from the Qing, and fight a later civil war.
4. The Taiping could be one form of the Union state, with perhaps it being the name of a theocratic government.
5. With the above, implement a theocratic government type, to be used in the above in particular, but perhaps in other places too. In all respects it behaves as a reactionary presidential dictatorship, though with a unique name and flag. I'm not sure if this is possible with the current engine though.
6. A monarchical government in China could simply be a new Dynasty, like the one Yuan Shikai attempted to (and failed) to implement. It's possible name is up for debate. Maybe Later Ming Dynasty, though Ming revivalists were few and far between by this point, particularly after the Taipings.
7. Taiping should be a one party dictatorship, with even chains to reform should they win.
8. Taiping should not be fighting merely to survive. On Independence they should always fight to eliminate the Qing, and at least assume rule over the Chinese Heartlands, if not the whole thing.
9. Taiping and Qing should not be able to exist at the same time, except at war. If the Taiping win, the Qing should collapse, perhaps forming Manchuria, with other parts going to other remaining ethnic states (EG Mongolia). That or the Qing should be annexed to the Taiping. It's not a secession war a la the American Civil War.
10. Taiping should perhaps have a unique religion, but this may be unneseccary considering the game doesn't focus on religion much. Protestant is fine.
11. Taiping should start with some social reforms, they were a radical proto socialist movement in certain respects. On the other hand their rule was quite haphazard at best. Your call.
12. Change the Chinese revolters. Increase their number so that there's at least one for every region. In case of Qing Collapse, they should all be driven to civil war to form the Union state. They could also revolt against a potential Taiping victory. They would also have each of the ethnicities as their primary cultures, thus preventing their getting assimilated away.
13. Chinese Union State could start with just cores on Core China, claiming the rest of modern day China with Irredentist decisions. They could recognise certain foreign claims for some kind of benefit (EG recognizing russias claim over vladivostok).
That's just a bit. I'm not a Chinese expert, but that's the stuff that leaps out at me. Some of it may not be possible with engine constraints, particularly government trickery.