You think China is doing diplomacy to make it easier for Japan, South Korea and Taiwan to get Middle East oil/gas? Without trade relationship with the rest of the world most Middle Eastern countries would literally starve or bake to death. China believes it can satisfy ALL those needs. Maybe it can! History says it can't.

You believe China, which is continuously threatening Taiwan because it doesn't like the friends Taiwan keeps is going to be fair about its new relationship with Iran/KSA/Russia? Not how China operates.

I'd argue China has practically declared war on Japan, SK and Taiwan. There's are very good reasons why it hasn't tried this before. If what you argue is true, then THEY would have had a seat at that table.