Great ideas! Yeah, a post-apocalyptic setting would work. I like the idea of the current meddling gods being ascended mortals. Maybe the process of their divine ascension was actually what "nuked" the setting resulting in rampaging elementals, the rise of megafaun, and magical mutations of humans resulting in the meta-lineagues and the like. There are many ways to integrate monks into such a setting.I think a post-apocalyptic framing would work well, which could explain the guns, megafauna, even gods.