I would like the Chinese to expand their wall, but don’t think I would link it to they hold all of China (all orig tt’s totaling 23 IPCs) would be very hard for China to reach, and too easy for Japan to grab one. Maybe you allow them more range based on how well the Chinese are doing, and can only expand their boarders if they reach a goal (liberation). They start w/12 tt’s valued at 12 IPCs total (but are normally down 4 on J1), and there are 11 IPCs more worth that Japan occupies at the start of the game. So if they hold say 15/23 original Chinese tt (could be a higher #), at the beginning of their turn, then they can expand into other tt’s TBD (see below). They wouldn’t have to include all 12 they start the game with, it could be a mix to get to 15/23 value, and they would have to have the min tt’s at the start of their turn. So they could lose some 1 IPC tt’s, but liberate the more valuable coastal tt’s to achieve expansion. I might also say that once they can expand they don’t lose that ability, because it could lead to a gray area if they start losing ground and get messy.
As for Mongolia, only allow the Chinese to enter Mongolia if the Japs or Russians break the Nap (activate Mongolia) under Alpha+3 rules (if the Nap is in tact then Chinese stay out). Also allowing them into the continental Asian tt’s works for me. India, Shan, FIC, Malaya and maybe Siam & Korea. I guess that China would get paid for Siam, and Korea (and UK tt’s if India was captured), and be able to place units there. Not so sure about the Russian tt’s though, would probably stop there to see how things go. And I guess you could allow the ftr to enter to sea (this might just lead to it getting killed though), but no China men on tpts, keep them on the Mainland (if you were thinking about it).