If Germany had kept supplying KMT China through the Second Sino-Japanese War, admittedly would have been difficult later on, the KMT would have certainly fared better.
in the OTL Japan was trying to come to some kind of terms? of course they weren't trusted. but if the KMT was in strong position?
Chiang pushed aside because he won't negotiate, Wang Jingwei becomes leader of Nationalist China much larger than historically?
probably joins the Axis? German u-boats based in China not Penang, not much other help for Axis? other than to threaten Siberia and railroad.
China much closer to Germany, adopts much of fascist ideology and techniques to consolidate hold over country. would expect the Nationalists to fare better against the Communists too.
one interesting spinoff? early German work on long range aircraft AND u-boats.