The Reaping

Question: What do you think about running a Bogovi story where Stvaranje and Khnum in particular are responsible for the world's overpopulation, and the Aztec gods (Itzli in particular) begin culling humanity for more power?

I think it sounds wacky and creative. My biggest question is this: how do the Bogovi fit in? When you say it's a Bogovi story, do you mean all the PCs will be Bogovi Scions, or is the pantheon involved in some other way? What are they doing in all this mess besides just being Stvaranje's usual targets? Considering that they're very much concerned with harmony, balance and the natural order of things, a situation like this could be very interesting for them; overpopulation on a large scale like that is a major problem for the preservation of the world's harmony, and it's conceivable that they might even have called the Aztlanti in to redress the problem (or, at least, aren't interfering directly). Then again, they traditionally disapprove of gods meddling in human affairs, so they might oppose such an idea on principle.

I don't know if you need Itztli to be a ringleader of the great culling; not only is the sacrificial death of humanity something that pretty much all of the Aztlanti (barring Quetzalcoatl in some of his moods) are on board with all the time, but Itztli himself is a pretty minor god, probably not more than Legend 9 or 10 in my opinion. He could make a cool guide or NPC contact for the PCs, though, sort of their in to the Aztlanti. At lower Legends, Aztlanti Scions that appear to be on purposeless murder sprees would be interesting allies and antagonists for your PCs, who may not realize what they're doing until the situation is explained to them; at higher levels, depending on how they decide to handle the issue, they might take it up with the Aztec gods themselves, or even decide to help them.

Khnum is a great choice for an antagonist for this kind of plot, because he really just does not give any fucks. The world gets overpopulated? Whatever. People are starving, he's causing way more problems than he's solving? Who cares. People want him to stop? Piss off. You might want to also consider getting the Pesedjet involved if he's the major bad guy; in particular, Ra and Ptah, as rival creator deities, might have a vested interest in seeing him stopped and provide aid to the PCs where they can. Unwary Scions might also have trouble pulling the trigger on Khnum, considering that he thinks he's doing, if not a good thing, at least a justified thing; you could also get some good mileage out of the story if the PCs decide to try to "redeem" him back to the side of the gods.

I think you have a lot of cool ideas going on there, even without involving any pantheons beyong those three (which you could do easily... anyone with Valor, for example, is going to have a problem with wholesale mortal killing no matter how good a cause it's for, and anyone might be worried about the prospect of the Aztlanti becoming more powerful than they are). Keep rolling with it, and I'd love to hear how it plays out if you ever run it!