I would make it prone enough to collapse that about 50% of the time the AI China collapses. The Rebels should be in Southern China, controlling/continuously retaking Shanghai and Hong Kong, for ease of European invaders. Also, the English, Dutch, French and Portuguese should be more prone to take such cities when available, and attack China/India/Japan/SE Asia more frequently. This would allow for Asia to finally be colonized, as well as make China really hard to play, but also, really fun.