Did you played CK2 recently, because CK2 works very well without having China on the Map, but it still exist has an Offmap Power, which is the best Solution.
Keep in mind, that the Clausewitz Engine can only support a certain Number of things, and that CK3 already likes to generate way too much Characters.
And also think of the Travel Events, how many more Rulers will exist, when China is added and how many Travels, they will start, which will spawn a lot of Characters.
Also, for an Simulation Game, the Game actually does not make a good Job at it, because it generates way too much Characters, instead of using the regular way for more Characters, by Marriage and Birth.
This also lead to the AI being incompetent, because the generated Characters, are always badly skilled Characters.