Lastly, all the Stan's left the Shanghai Pact about a month after the events put them in it??? Russia, PRK are still in it though so it's basically the same problem I had with the original where the Stan's, Myanmar, and even Vietnam would abandon them...
I think something has to be done with AI to fix this problem. When Shaghai Pact formes and everyone who is invited accept, members are: Russia, China, Kazakhstan, Uzbekistan, Kyrgizia and Tajikistan. I experienced that Vietnam joins later via events, but I didn't play long enough to see if DPRK and Indonesia join the alliance.
As for leaving members, Tajikistan is worst case. I never experienced some other nation left SCO except Tajikistan. They just break alliance soon after they accept invitation.
Maybe little event chain can be made from this problem? Tajikistan joins SCO, but they leave due to American pressure(NATO supplies it's troops in Afghanistan from Tajikistan). SCO has event about rogue member and calls for intervention. You could chose few options, such as ''we don't need them'', ''this means war'' and ''launch convert operation''. This crisis would not be important enough to start war with West, but it would damage relations of SCO nations with USA, especially if SCO performs open intervention(war). If there is a war, Tajikistan is puppeted by China after anexed. Convert operation(some kind of coup or revolution) has 50% chance for success and Tajikistan is puppeted without the war. If SCO ignores situation, relations with West improve.
Western influence in Central Asia could be simulated with US military access in Tajikistan. When Tajikistan is couped/puppeted, military access is revoked(other option is to make higher partisan activity in Afganistan due to lack of supplies for NATO instead of messing with military access). I remember similar event chain like this was working well in 1.5. Story was about American airbase in Kyrgizia. I know this is maybe less important thing for team to do know, but modern day crisis are mostly done in this way. To reach global war, many smaller actions has to spark full scale conflict.