Holy cow, Dieter -- I missed this post earlier, but it's a brilliant idea. In my just-revived DragonMech campaign, I had slowly been setting up a gnoll cult as the Big Bad: worshippers of Yeenoghu who have been secretly working to aid the lunar gods' efforts on Highpoint. Gnolls - baying at the moon - lunar agents, right?
But what if the truth is that the cult is actually working against the lunar gods? When the lunar gods came to this cosmos, they kicked Yeenoghu off his seat of influence, and his followers are desperately seeking ways to restore his power.
Replace Oniukh and orcs with Yeenoghu and gnolls, and this could work. It'd be a great way to mess with my players' expectations and nothing that's happened in the campaign so far would contradict it; it could even fit together perfectly.