If the "lead" blasphemies really can spawn others simply because of how intense the negative dynamis that comprises their being is, I could see the situation in Corvos being pretty awful still.

I wouldn't mind a Bozja-like structure if it has us having to purge blasphemies from ruined settlements; perhaps Bozja-esque aesthetically, but not quite as desolate due to the place not being an active warzone.