This a a fairly obvious divergence that for some reason doesn't get talked about much. What if the Tairan clan had managed to consolidate control over the Japanese government in the 12th century? The specific POD could be a Taira victory in the Genpei war or, alternatively, Kiyomori killing Yoritomo and his brothers after the Heiji rebellion, thereby avoiding the Genpei war in the first place.
What would be the consequences of Japan being led by the Taira instead of the Minamoto. The first, obvious one, is that there would be no shogunate seeing as the Taira were seemingly planning to exercise power through the imperial court, much as the Fujiwara had before them. So we're still talking about a transfer of power towards the samurai class, but probably not a whole parallel administration like the Kamakura shogunate. We'd simply see more samurai (especially those belonging to the Taira clan and their vassals and allies) being appointed as provincial governments and government ministers and intermarrying more with the imperial and noble families. The second possible main divergence that I see is related to foreign trade. Kiyomori's grand plan was to move the capital From Heian-kyo (in modern day Kyoto) to Fukuhara-kyo (in modern day Kobe), a port city. His intent seems to have been to promote maritime trade, especially with Song China. While it's hard to predict the policies of a whole dynasty of rulers over the course of decades and maybe even centuries, it does seem to be a general rule in Japanese history that clans from western Japan (where the Taira and their allies had the most influence) were generally more interested in outside trade. With this in mind, would a Taira-led Japan be a more outward looking Japan?
What would be the consequences of Japan being led by the Taira instead of the Minamoto. The first, obvious one, is that there would be no shogunate seeing as the Taira were seemingly planning to exercise power through the imperial court, much as the Fujiwara had before them. So we're still talking about a transfer of power towards the samurai class, but probably not a whole parallel administration like the Kamakura shogunate. We'd simply see more samurai (especially those belonging to the Taira clan and their vassals and allies) being appointed as provincial governments and government ministers and intermarrying more with the imperial and noble families. The second possible main divergence that I see is related to foreign trade. Kiyomori's grand plan was to move the capital From Heian-kyo (in modern day Kyoto) to Fukuhara-kyo (in modern day Kobe), a port city. His intent seems to have been to promote maritime trade, especially with Song China. While it's hard to predict the policies of a whole dynasty of rulers over the course of decades and maybe even centuries, it does seem to be a general rule in Japanese history that clans from western Japan (where the Taira and their allies had the most influence) were generally more interested in outside trade. With this in mind, would a Taira-led Japan be a more outward looking Japan?