I don't really have anything to add except to point out that we don't get (I don't think) any internal monologue from Meppa. I think this is significant, because an internal monologue would portray what a character 'really thinks.' I think that we can trust Kellhus to be accurately portraying himself to the reader in his internals in PON (he doesn't do it in AE) but for any character that we don't hear their thoughts--anything about their appearance could be deception.
WTF Meppa, he could be just about anything...maybe most of all a decoy. I wonder if Bakker has kept loads of Cisharim alive, but the reader is deflected from the possibility because 'Meppa is the last.' With old Moe having oodles of time before Kellhus arrives, I wonder if he swelled the ranks (making sure to keep the scarlet schoolman deceived of the numbers) so Moe can go on manipulating the world without leaving a mark.
More speculation: what if all of the cish who died in the holy war were just the ones that did not belong to moe's faction, so he controls the remainder; what if some of the cish went north to Ishual when the fanim and scylvendi warred; what if moe has figured out a way to be blind and yet appear to have eyes (the cish are everywhere--like xinemus, but they know how to 'look' like their eyes are opperative?
EDIT: breaking up the text