I had the same theory but with Cnaiur rather than the initiate.
Remember Moe says he needs Cnaiur's strength just before he gets choraed, and Moe's snakes are pressing hard against his temples...
Cnaiur's or Moe's arms would give either of them away because of the swazonds.
However, it is Meppa's skin tone that messes most theories up.
He's brown and the Kian and most surrounding peoples are pale (Ketyai and Scylvendi). As are Moe and Cnaiur.
Malowebi should surely have been surprised if he were Zeumi.
He could be from Nilnamesh, I guess - can't remember them being described as any particular tribe.
Another interesting thing, Fanayal is a direct descendent of Fane and the Cishaurim were synonymous with the Kianese tribe, the Indara-Kishauri (water-bearers) who saved Fane's life and attended his revelations. So Meppa and Fanayal should be fairly closely related, at the least in a social setting. Meppa may not know who he is, but Fanayal should.