Well, apart from i agree with Katsyev (the underpowered Poland, Russia&Ottomans (you know, Johan, the unit prices in EU I were huge advantage, and there were no negative events), i am also big fan of AGC Indian setup-ie, no colonizable provinces.
IMO, its better from MP perspective, too, as having European religion and culture provinces ends with India split between Europeans in XVI century. If there would be no such provinces, and if Mughals would be played by Human, i doubt we would see more than few footholds gained there until XVIII century.
AGC also made most of Indonesia nation-states, and i am unsure if it would be better from MP perspective. This pretty much prevets Portugal from doing much there, but i think Holland could do it. And again, no Euro cultures/religions there is good thing IMO, same with harder coloniztion/conquest there (although it wouldn't be that much harder with small AI countries. Still, shipping troops from Europe with low naval tech is very costly endavour....)
The reason i suggested China is entirely from MGC4 Sweden

Seriously, i wouldn't be so fast to add countries for that reason. For example, i think Ottomans deoesn't need beign stopped-i rarely see them gaining anything from Hungary (and i think it would be good thing), MGC 4 was again exemption in this case.
And, while we are at it, what do you guys think about turboannexation (ie:fall of governemnt)? Without BB wars in MP, it wasn't that bad, now it becomes the worst nightmare, allowing countries (especially Spain, which doesn't have any revolters in America), just to say "no" to every peace offer. France would probably want NOT to control any Spanish provinces in such case, 3BB is very high price.