If, instead, you allow US player to simply built up to 2 Infantry per turn on any Allied chinese territory
That works OK, Baron – I’d prefer to the OOB rules. The problem with building infantry is that it doesn’t create an interesting choice for the US player, and if Japan kills the Flying Tiger on J1 (as it always should without an American bid or a radically intense Russian reinforcement gambit), then China never has any offensive potential no matter how much Japan under-invests there. Right, like let’s say on turn 1 I kill just Szechuan, leaving you with 4 infantry. You build 2 more infantry, now you have 6 infantry. So…so what? I’ve got something like 6 infantry, 2 artillery, and 2 fighters in the region; you don’t have any interesting counter-attacks.
With an IC, America can choose to build infantry (standard play) or something aggressive like a tank or fighter (Chinese gambit) or build nothing at all and save the IPCs for the ocean (Atlantic gambit).