. . . At some point in history that would be the Tocharians, right? That would be interesting...and rather bold of Firaxis.
"Tocharians" from roughly 1500 - 2000 BCE to 6-800 CE, although apparently the archeologists, linguistic studies folks and cultural anthropologists can no longer agree on where they came from, exactly which of 3 "Tocharian" languages was used for what (at least one is argued as a strictly liturgical language, but even that is uncertain). The points of agreement remain, however, that they were "Indo-European/Turkic" and that they built some very impressive cities - up to 80,000 population - that relied on extensive irrigation works to survive on the rim of the Taklamakhan desert. They would make a lovely choice for a Trade and Religion Civ (Kucha, the largest of the cities and possibly a regional Capital, was also a major center for Buddhist studies in the late Classical Era).
The problem, as with some other Great Candidate Civs, is finding named Leaders. Although, at last count, there are over 7000 known Tocharian manuscripts, the great majority are religious writings and texts that don't tell us much about politics or internal history to give us a Leader selection.
The area was later the center for the Kushan and Uyghur Khanates, so I could see including them as part of one of those slightly better-attested Civs, or, at least, add Kucha as a Religious And Trade/Commercial City State that rapidly spreads whatever Religion it gets to every city of Civ connected to it by a Trade Route. An Alternative Jerusalem with camels . . .
I've been fascinated by them for some time, since they are a rare example of a definitely settled, 'urban' culture/Civ and population right in the middle of the so-called "Sea of Grass" steppes supposedly entirely populated by horse nomads since 1000 BCE.
I could've used your help in writing a Social Studies essay about the fall of the Roman Empire back in Freshman year of High School. I struggled with it (my local library had few books about it) and got a bad grade.
But I agree the Huns are a "One Shot wonder" and I'm not forward to seeing them return in Civ7.
I took a minor in Education at university, but never officially taught in any civilian school. On the other hand, when I worked at Barnes & Noble, we would occasionally get some young person or family come in and ask what we had on a subject that they had to research for school. If it was anything historical, I got the call and would show them what we had and give them a critique of which books were most useful. My favorite was the afternoon a woman came in with her Junior High School son who had to write a report on the Battle of Kursk. It was a potential 'candid camera' moment, because I not only found them a half-dozen references in the store, but had them come back the next day so I could give him copies of my lecture notes and slides on the subject from when I lectured on the battle at the Gaming Artists and Manufacturers convention in Ohio a few years before!
He got an 'A', by the way . . .
And as said before, while the Huns are probably well-known, there are lots of other better and longer-lasting Predatory Pastoral Civs that could take their place in the game: even the Scythians, in fact, are a better choice, also Goths, Pechenegs, Kushans, Seljuks, Commache, or Lakotah would be more 'flexible' choices, with a variety of Civ-traits that could be turned into UAs, UUs, or UBs.