Not to toot my own horn, but this is part of my District Overhaul mod. Districts and buildings no longer give GPPs at base, but specialists do. Also, in general, Tier 1 buildings get 1 specialist slot, Tier 2 buildings get 2 (though the Temple gets 3), and Tier 3 buildings get 2 (though Religious Buildings get 1). (I haven't touched UAs and beliefs like Divine Spark, however). See above. While @criZp has noted it's bugged, it does work, somewhat, and I've seen the AI use specialists to rush Great Prophets, so yeah.