I think a victory of Japan, and conquering of Quingdao would deny the possibility of a 1937 war. Only if China attacks. Japan wouldn't move forward until they pacify the territories. They will have too much problem with Chinese than to initiate a war so early again. (Manchukuo and Quingdao would be too much of a land-grab for them.) Pacifying Manchuria was a nightmare for them, and never really happened, so a territory in the mainland of China would be a true horror. They would need a large number of armed forces just to keep the peace. Also there could be a few events about how to deal with the Shandong clique remnants and the local triads. Dissent and revolt risk would be sky high in Quingdao, but if they take in the former local warlords in the General Government, than it would be lower. The problem would be, that its quite possible, that in case of a China and Japan war, they would try to initiate a coup to join China, or stay neutral like Xinjiang.
If you could think of a way of helping the Ma family with the Japanese, than the Ma could be a serious problem for China. They would try to annex Xinjiang, and take Tibet. Their cavalry army was quite fearsome and dangerous, and their military commanders were some of the best. While Ma Bufang was an autocratic leader, others always favored imperialism and royalism. One of the Ma leaders would surely try to be the new emperor, or support one of the possible ones, but not Puyie. They despised him.
Possible emperors: Kung Te-cheng (Confucian descendant)
https://en.wikipedia.org/wiki/Kung_Te-cheng http://news.iqilu.com/kongzi/20150725/2495622.shtml a lot of pictures are here, if you need them for events.
Zhu Yuxun (Ming descendant)
http://www.cdsl.gov.cn/653.html
Yuan Keding (Yuan descendant)
https://zh.wikipedia.org/wiki/袁克定
Zhu Rongji (Ming descendant)
https://zh.wikipedia.org/wiki/朱镕基
Possible Ma emperors:
https://en.wikipedia.org/wiki/Ma_Zhongying https://en.wikipedia.org/wiki/Ma_Qi
The Ma family would not try to unite China, just take the northern and northwestern parts.