Another idea--Yamato lives
I just had a different thought on keeping Yamato. Suppose that, just before the invasion of Okinawa, the Emperor decides to intervene, and manages to survive the decesion intact. His proposal: Japan renounces claims to all but the Home Islands, removes its troops, and accepts the following:
Small army, numbers and equipment limited by treaty..sufficient for a home guard, esentially. (This has the internal benefit of completing the removal of the army from its role running the country.)
Aircraft limited in quantity
Navy to consist of one battleship, 3 cruisers, and a small number of destroyers. No warships that can carry more than 6 aircraft, and no submarines. It's more a symbol than a real navy--just enough to say, "We're a real country still"
Japan to allow American troops to inspect, an occupation in all but name.
The whole idea on the part of the emperor (or some advisors) is to end the way with a token military, so they can save some face from a negotiated setlement, rather than be destroyed as a nation. Perhaps Japan could even pay some reparations for "The actions of criminals that subverted the government of Japan" publicly placing a lot of the blame on Togo and company.
Normally, that wou,ld be a no-go...but there have been setbacks in Europe. Either Stalin was killed, and Sovoet in-fighting has severely hindered the Soviet war effort--Germany is doing better there, or D-Day was a catastrophe, perhaps weather related. Peace in the Pacific would allow more forces to be deployed to Europe, and headlines like "JAPS SURRENDER!" would not do the allies any harm...
Now Japan has a token navy, including one impressive battleship that's turned into a symbol of Japanese pride.