Given the current and future trajectory of geopolitics, it makes a lot of sense to develop CR929 mostly relying on Russia and China suppliers or international suppliers with minimum sanction risks.
China actually has the capabilities to replace/develop many of the western subsystems in C919, even though they may not be at the same level. The logic of selecting suppliers back when C919 started was within a context that was quite different from the reality of today. For CR929, they should start with a development plan that is largely sanction-proof. Together, Russia and China can do that. However, they probably should make the engine choice flexible and optional, because both Russia and China have their own engine development programs. Having the option of choosing a western engine should also be helpful in selling to international market down the road.
In addition, if CR929 is developed mostly based on Russia and Chinese suppliers and subsystems, then CR929 can be considered for military uses right from the beginning, which may subsidize or lower the cost of development somewhat.