You might be right about Turkey. Would depend on the opportunity available and the relative 'cost' of taking advantage.
The other thing about China is for a long time Soviet influence in what is now Xinjiang province was quick significant. There were even a few conflicts in the area, proxy wars etc. No idea what the balance of power was like in the 1920s.
Without Soviet intervention, Mongolia might have been a bit odd. IIRC it ended up being the Red Army that tipped out Ungern Sternberg from Mongolia, so without a strong state to remove him from power (China wasn't in a good position to do so at the time) the already bizarre tale of "the mad baron" could have gone on even longer.
For Japan it would be mostly a strategic consideration - push Russian influence out of the Pacific, expand the foothold established in Korea which might in turn open up opportunities in China. There wasn't much in terms of natural resources at the time available. Apparently some of the bigger industries set up offices there, but I don't see anything about them starting any big projects. The intervention at the time was quick large and ran until 1922:
http://en.wikipedia.org/wiki/Japan_duri ... tervention