The south asian and east asian nations are seen by myself and probably most players as 'easilly annexable provinces' that since they have a different religion dont have a big BB effect.
There are two possible solutions.
1) Make them all natives. This means that the first COT appearing in buru, ceram or jakarta does not get 1500o of chinese trade. Make them all hostile so if you want to take any chinese province you are going to have to struggle a long long long time and spend a lot of money and a lot of troops before getting anything. This makes the TPs in Nagasaki and Canton possible for The Netherlands and Portugese.
2) Give them big buff forts and really really really cheap troops. (plus good generals for when the europeans arrive to conquer). Level 4 forts D;D;D;C;C;C construction costs for units will make china, japan and the SEAsians dangerous to the europeans. The europeans will have to consider diplomacy as opposed to just marching a mediocre conquistador with som inf, cav and cannon and take all their provinces.
3) Nationalism, this is my favourite and most elegant solution. This is probably NOT possible for the IGC. Have increased nationalism for non europeans. So instead of 3,2,1 over 30 years as it is in europe have 12,11,10,9,8,7,6,5,4,3,2,1 over 120 years. You bet your right patootie that nobody is going to bother with china then. Just imagine provinces larger than flanders revolting once per year with 100,000 troops with your technology??