Instead of timelines about empire building through conquest, I'd like to see one about a region or subset of a kingdom/empire that becomes more and more autonomous that it basically becomes its own nation in all but name. In OTL Japan, the Northern Fujiwara clan ruled the northern third of the island of Honshu and their capital at Hiraizumi rivaled the imperial capital at Kyoto in its splendor. In an ATL I'd like to see this clan become even richer and more autonomous than OTL by monopolizing the fur trade with Hokkaido, Sakhalin, and coastal Siberia. As time progresses we'd see how Japanese trade goods and technology transform the fortunes of the eastern Siberian tribes, which would impact their neighbors in Manchuria and Mongolia.