I’m not to sure about the Chinese getting an IC to build ships etc…
I have a couple quick thoughts:
Maybe give the Chinese a capital in Szechuan (minor IC), and if the B-road is open allow them to build units that cost 10 ipc or less inf, art, mech, AA gun, tank and flying tiger. Limit them to just 1 AA, 1 tank, and 1 tiger max on the board, but allow them to replace them if lost (they start with the flying tiger, but can replace it if it goes down). The Chinese can also buy inf and place in any Chinese territory as by normal rules for China. If the Japanese get the capital (minor IC), it remains on the board, but can’t be used by Japan (IC represents supplies sent by allies, not manufacturing). Japan would get 1/2 the Chinese income (rounded up), and the rest China keeps (to purchase inf as normal for any Chinese held tt). The part that Japan gets can be spent in Japans place units phase of that turn in the former Chinese capital (raided the allies lend lease supplies), or can be added to Japans bank (or allow to split between the two Japans choice). If the allies regain the Chinese capital (minor IC), and the B-road is re-opened then things start over, and the same events can happen. You might have to boost the Chinese starting units a bit so they don’t lose the Szechuan capital to easily (but maybe not).
I would also look at giving the tiger +1 in attack and def, and maybe say it can’t be used in attacks unless the B-road is open (fuel supply). Read that in someone’s house rule, and it sounded cool.
edit:
Could even do a US lend lease. Something like in the US purchase units phase they can send up to 5 IPCs to India to hold for the Chinese. India receives it right away, but can’t send it to china until after UK’s turn (China has to wait a full turn). On the Chinese purchase units phase (following the UKs hold turn) India transfers the lend lease to China if the B-road is open for China to spend in their capital. India can’t hold more then 5 IPCs for Chinese lend lease, so if backed up the US can’t send any. The Lend lease is subject to axis intervention. When the US declares they are sending it, the Japanese player roles 1 dice. Role 1-Japan gets it (captured), 2-3 shipment was lost (return IPCs to bank), 4-6 it arrives safely. Of course if India is captured, any lend lease IPCs would also be captured. Capturing axis power get to spend the lend lease IPCs in that turns place units phase in India (captured supplies) or for ease just add it to their collect income (or allow to split between the two axis choice).
As far as leaving China hmmm…
If the B-road is open, and both Hong Kong, and Shanghai are in allies hands they can enter any tt that borders China (would include a handful of Russia territories, FIC, and Shan State BTW), or any Mongolian tt (if activated). Don’t want them to get deep into Russia.
Just my 2 cents