LLM's should be great at generating concordances and reference checks through vast bodies of boring literature that no one wants to read. In other words, most of the everyday clerical grade work of professional theology.
Similarly bodies of law and regulation; I'm surprised no one has shown off their "federal register" based search and "understand this for me" bot yet. the source material is vast, very well organized, and free. Probably the fact that there's paying customers available has kept such efforts quietly commercial.