Is there a reason why most China unifiers can’t join factions?

I feel like this is what brings down gameplay in China the most, in a World War II grand strategy game you don’t really get involved much in the actual war. Lore wise I can see why any Chinese would be somewhat isolated from the world and would mostly focus on rebuilding, but I think you could say the same for America. I think given how Russia backs anti-concession Zhili it makes complete sense for them to be able to join the Moscow accord and help finish off German East Asia. I think other powers would be more of a stretch but I could see federalists joining an American led entente similar to the Ottomans or they could be backed by anti concessionist russia. I can see why balance wise it could also be annoying to capitulate China but I think if the option to join was far down the post unification tree that could be mitigated.