That's actually what I was thinking of; maybe a series of scriptures based on the Queen of Sheba (or a male descendant) being prophetic? Or a traveling preacher type who (through conversion and force of arms) convinces the Ethopians (and Nubians/Sudanese/Copts even, I suppose) that his line is actually the Solomonic line?
Hmm... I like this, lets develop it further. Maybe this ATL prophet appears in an unstable period of Ethopia (wasn't there few periods of chaos?), and starts uniting the country.
See, I don't like doing concepts that I
KNOW other people have done before, for fear of comparisons (whether through people reading my work and comparing it to others, or myself judging my own work), so though you're right and Central Asia is probably the best idea, I don't want to do something similar to your TL. It's a pet peeve of mine; I'm fine with other people doing that sort of thing (lord knows its almost impossible to avoid accidentally doing a TL idea that nobody else has had), but I try to be as original as I can with my TLs.
And sorry for mistaking you for NomadicSky; though with your Tengriism TL and the name "NomadicSky", I think it's a reasonable mistake to make!