PainState I really like the way you think this into the bigger picture.
I think an all in buy towards china R1 is a bit to risky and not necessary. Coming in a bit lighter ground forces wise and instead supported by all 3 Russian planes (which can easily be pulled back if needed) would do the trick to.
Supporting Yunnan is still better than going north in my opinion. It can easily be stacked by China Russia and the brits.
China rarely own Yunnan at the beginning of C1 and can therefore not buy any artillery.
Now china can support them with some INF and they will be able to “can open” for Russia in the north. Another issue Japan will have to contend with IF China is supporting the Russians and not just throwing every unit they have into the vortex of death in Yunnan. ** foot note **: Should China on C1 build all ART and place them in the north to support this plan?