Even if that was true, which it isn't: Bannerlord is based on the early middle ages, meaning from ca. 500-1100. The Islamic conquest of India didn't really begin until around 1200.
The ironic thing is that atleast until the Kushana period, modified versions of Greek breastplates with pteryges were still employed:
Indians are actually a great idea! While I don't see an entire African faction working for the map, but, as proposed before, merely as an Aserai sub-faction, I could imagine a faction bordering the Southern Empire, the Aserai and Khuzait. It could be a mix of Sasanian Persia, Persianized Huns, and, most importantly, ancient Indians like the Gupta. Lots of golden jewelry, exotic weapons, bare chests and unpronounceable names.