I feel like the Fetishism mechanics would be a very good framework for the various Folk Religions across the globe currently represented by Generic Animism. Alcheringa already works very similarly, but by working through events rather than a mission tree, Fetishism is more easily adaptable. Instead of creating whole new religions and religious groups, it would be enough to create a few new cults for various regions.
Playing around with the Console, I did for example change the religion of Madyas to Fetishist. Fighting through the Philippines, you'll get access to the Cults of Buddhadharma, Sanatana Dharma and Islam. The native cults are obviously bullshit, defaulting to South African Cults, and the event texts keep referencing Africa, but new ones could be created for that (and/or existing ones could be adapted: a Fetishist Madyas with the Hindu cult already unlocked is probably more representative than a Hindu one with Animist provinces at the start of the game).
Playing around with the Console, I did for example change the religion of Madyas to Fetishist. Fighting through the Philippines, you'll get access to the Cults of Buddhadharma, Sanatana Dharma and Islam. The native cults are obviously bullshit, defaulting to South African Cults, and the event texts keep referencing Africa, but new ones could be created for that (and/or existing ones could be adapted: a Fetishist Madyas with the Hindu cult already unlocked is probably more representative than a Hindu one with Animist provinces at the start of the game).