tristrem asked: "Will China support Iran in a war with the West? Will China actively oppose the arming of Taiwan with advanced weapon systems?"
You should know the answers to both of your questions are "No". In fact, the China government has been the true supporter of arming Taiwan with advanced weapon systems. China is the major income source of Taiwan.
Now you should remark on the "preventive war" that the China ruling elites have launched against Chinese. Click the links: