I haven’t done an exact count of the Chinese starting pieces, but just by eyeballing it, it sounds to me like you’re stretching China way too thin.
You send 2 infantry to Hunan C1 and 6 infantry to Yunnan C1 – that’s most of your starting pieces. When you “stack up” in Szechuan on C2 after building 3 artillery, that means your stack is what, 4 inf + 3 art? If that?
Even if Japan only landed part of its air force on the Chinese coast and Chinese coastal carriers (e.g. 12 planes or so, no special prep), that’s still a pretty good battle for Japan. Your Chinese armies only defend at 2, and the planes attack at 3.5, so 12 planes * 3.5 = 42 pips = 7 expected hits, i.e., you can expect to wipe out a stack of 7 Chinese armies in one round of combat. Those 7 armies only have 14 pips to fight back with, so you’re losing 2, maybe 3 planes in exchange for what’s left of the Chinese stack.
I see those as totally acceptable losses, especially if Britain has exposed itself by stacking Burma, sacrificing ships to block SZ37, and so on.
I agree with you that trading Chinese infantry 1:1 for Japanese planes is a great deal, but you’re not going to get that deal if you push China forward so aggressively in the first couple of turns.
If British India is very strong, then even losing 3 planes might be unacceptable, because you’ll need those extra planes to be sure of taking India on J5 or J6…but with the British navy gone, the British expeditionary force in Burma / French Indochina doomed, etc., then India will fall without too much extra effort, so the planes you lose demolishing China are expendable.