This is going to be very hard. There's not a lot to work with between ~1864 and 1899, considering this is the conservative era of Cixi, especially after the 1870s when almost all of her primary opponents had been killed or removed from power, and the ascension of the Guangxu Emperor, who was Cixi's puppet in all-but name.
Your best bet for anything might be the Sino–French War. Perhaps someone other than Sienkiewicz is in Tokyo, and the Franco-Japanese alliance is carried out in late '84, meaning that the Chinese are now effectively fighting a two-front war, which means that both the Fujian and Beiyang fleets are destroyed, and the Qing face land invasions from Vietnam, Korea, and up the Yangtze and Yellow rivers. You might see a domestic Boxer-esque uprising take place against this background against both the native Qing and the invading Japanese & French. I've seen it implied in numerous sources that the original Black Flag armies might have been remnants of the Taiping, Miao, and Panthay rebellions that had fled south across the Viet border and merged into the native Vietnamese resistance movements there; there's no reason that they couldn't move, once again, back north in the face of encroaching French arms.