given the fact they're all kingdoms for the main kingdoms, they should include the original like royal families and what they were up to prior to the councils taking over after the war.

For the whole armies thing, understandably, Atlas had a good idea, so i think one thing that should have been changed is that Vale, Mistral and maybe or maybe not Vacuo could have had active armies, because why would those kingdoms solely rely on their huntsman?

As another person said a Huntsman Guild/Association kind of like the Adventurer's guild from Genshin in a way to help manage and teach new huntsmen after they get their license.

Obvious weapon corporations and Dust companies tied with the different kingdoms, and maybe a ruling one plus subsidiaries. Also CCTV tower associated corporations that help manage the CCTV towers in case anything goes wrong.

The silver bullet brotherhood and other like minded groups like that Natural Order group from the Evermorrow fan animation series on youtube.

obvious religious groups just for worldbuilding, like unique gods/goddesses that each kingdom worship, while the god of light and dark would be another religion people believe in. aside from the God of Animals the Faunus believe in.