IMHO even if the Pacific campaign proceeds more rapidly, let's say Okinawa done 6 months earlier, I vote against the invasion of Japan. The Navy and the USAAF were against the invasion, it was Mac who was the biggest advocate. More blockading/bombing earlier - with Okinawa 6 months early you can have B-17's and B-24's as well as mediums bombing Kyushu for sore, and perhaps parts of Hokkaido given the distances. During this time you might see Korea or Taiwan invaded to "close the ring", if Korea is taken there is no way the USSR occupies any of it, as in winter/spring 1945 they are still occupied advancing against Germany. In fact, it is certainly possible that if the US takes Korea in the spring/summer of 1945, Chiang might just have troops brought there to attack across the Yalu against the Japanese (who are now cut off) and it also allows him to get a legitimate foothold in Manchuria which here can be supplied through Korea during the civil war as opposed to needing US air transport.
Another advantage to the six month advance of the timetable is that defense in places like Iwo Jima and Okinawa are less complete, and the flow of reinforcements and materiel to these (and other) spots is reduced making these campaigns less costly.
While the personality/persona of MacArthur was of value in Japan, I agree with the poster who said essentially all of the reforms/reshaping were the work of the bureaucrats/New Dealers who did the work. No matter who was the American shogun, the Japanese were going to toe the line.