I've heard an argument that what saved the Qing in the mid-19th century was the Taiping. By the 1850s, between internal weakness and foreign exploitation/embarassment, the dynasty wasn't in the best of places. However, the Taiping were so monstrously horrid and so alienating to provincial elites and western powers alike, that provincial elites opted to rally around the Qing.
If a rebellion had come from a less insane source, it may have succeeded and a new dynasty could have been created.
So who else could have revolted against the Qing in the mid-19th century? What would such a dynasty have looked like?