The Tanguts are a civilization that specializes in cavalry, with unique abilities such as generating gold from hunters and having free blacksmith technologies.
They also have a strong defensive garrison and a team bonus that grants armor to trade carts and cogs.
The Tanguts’ unique technologies include the Trekker infantry unit that ignores elevation bonuses and a Hooked Harness technology that transforms killed Iron Hawk cavalry into Wailing Iron Hawks.
The Tanguts lack Hand Cannoneers, Bombard Cannons, and advanced economic technologies, but have access to strong cavalry units, siege onagers, and a basic navy with Fast Fire Ships.
The Tanguts were known for their ambush tactics and had established their own empire before being conquered by the Mongols.
I think blacksmith techs available one age early is a better Civ bonus.
The Civ would need to not have access to bodkin. (Replace your Imp UT for a defence +3 attack for ranged units to make up for it.) Hooked Harness just becomes built into you UU.