The Xia are still a different issue all together and could probably use my earlier suggestion of a dynasty related decision to raise some troops and a special option to fight a less massive war with china for wealth, men, and artifacts. I think what needs to be done now that you brought up the Jin-Liao connection to have a Liao invasions similar to a weaker mongol invasions for starts before 1066 and a trigger that allows Jurchen invasions to start after that point, with the typical game rules to set them as random or historical as usual. even though the southern border on the eastern side of the map is technically bigger. When the mechanic was revealed I expected the Song to count as the true emperors of china but I guess whoever owns the north gets the title. I wish an even would just form a second chinese empire to communicate with so both can be represented. Honestly the Song just disappearing kind of sucks. I wouldn't be surprised if the devs and beta testers played mostly in 1066 and figured the early Jurchen invasions were fine. The Jurchens become the emperor around the 1111 'bookmark' but that leaves the song to something like 100 playable years.

Ck2 chinese imperial government