New NPC factions...

[Asymptotic]

I know a little bit about pre-Sirius fluff... it was basically Latinos, Americans, Germans (one assumes the French were annexed into "Rheinland"), and the Japanese against the Chinese, Russians and other Far Eastern powers.

The vanilla FL fluff says that only the Alliance sent sleeper ships and the four Houses that exist are the ones who survived. (Kusari is JAPANESE ONLY!)

What if there were a terrorist faction opposing the Coalition who constructed its own sleeper ships, albeit smaller, and they landed in the border worlds?

Also, on the Xiongnu: You're close on the "Mongolians" guess; they were both nomadic foreigners who threatened and encroached on China's borders. However, the Xiongnu originated not from modern Mongolia but from the Caucus mountains (they were known by the Romans as the Huns and by the Indians as the Hunas). The regional names that they were known by differ, but the idea is the same.

China and Japan have been (relatively) bitter enemies ever since Japan invaded in the early 20th century, especially in the Rape of Nanking. Thus it would be most reasonable if the Xiongnu faction finds its roots in the Barrier systems (very similar to the mountains from which they originated on Earth.)

Phew, ^long^.