Trying looking in NRP then.

That said, I put alt-history down as one of the more difficult things to tackle since simply saying "X" tends to ignore a plethora of other factors at play. Per Song-era China: they were falling apart as they were during Genghis Khan because the Song Dynasty had lost the Mandate of Heaven, or the Chinese ideology of who has the right to rule and their authority had pretty much eroded; which is why and how the Mongols could take advantage of them.

Personally, the only alt-history I have the patience for is Precipice of War, if because it's been going strong so long we've learned to work out the peculiarities of the core premise so it presents itself as being more coherent. Having said that: I do appreciate seeing more in the way of fantasy RPs. Alt-history RPs come with a lot more baggage than people tend to anticipate to make a workable premise. It's not really as simple as saying "X-changes so Y-continues in a different direction".

So back to the case of the Song: their authority and right to rule had eroded or was beginning to erode enough that another Great Khan would eventually sweep in and take what they wanted from China. But really: Mongol rule in China wasn't really regressive. That was the Ming.