To come back to the OP a little bit, what if Hirohito and the Imperial Japanese armed forces heed Yamato's warning "I can run wild for six months … after that, I have no expectation of success"? They take the Philippines and immediately after send a peace treaty offer to Washington and Australia? Something along the lines of:
1) Japan will immediately return all captured US troops
2) Japan and the US will stay on their own side of the International Date Line
3) Japan will have free reign on the mainland (including the Malay peninsula / Singapore), and Indonesia is now "neutral zone" with Australia?
I'm not sure the Aussies would be happy, but I think the US would take it. Gives the US time to beef up Pacific defenses, while fully concentrating on Europe.