As you already own China’s VC, I don’t think China is as important although the early plays preserve how long you have before China comes back to try to take it. They are “easy” territories to take, which makes them appealing. However, just taking Borneo alone is worth the same IPC as all 4 “plays” in China on Japan1 and its basically free and much harder to reclaim.
If you push as far in as you can on J2 and withdraw backwards playing “turtle” to Shanghai, you can buy yourself to at least J5/J6 before China is knocking on its door. Japan can win in VC’s by that time, or be very close to it with a Sydney sack on J3/J4 instead of committing the northern mainland units to China).
Plenty of better uses for those fighters scattered around the mainland, and more VC’s (Manilla, Calcutta, Sydney, Hawaii and Defending Tokyo)