Since you're working on Holy Fury I have some ideas with the mechanics.
Bloodlines: Have one based off of each sage from OOT as well as one based off the Zelda from Skyward Sword
Great Works: All the temples and dungeons can be made into Great Works. Great Works can be burial grounds and hold relics. Those relics would be the various things you find in dungeons such as legendary weapons and the medallions.
Warrior Lodges: There's another mod that makes Knight Orders using these mechanics. Knights of Hyrule, Sheikah Assassins, Zora Knights, ect
Sainthood: It could be used for past Sages, Zeldas, and Links.
You mentioned off map powers so I got a few ideas. Subrosia, Lorule, Picori. I know you mentioned Termina and the Twilight realm being on the map, but both would also be good for off map powers. The twili wouldn't be found in the main Hyrule too often so you could populate the main map with them using the invasion mechanic, asking for specialist, royal marriages, ect. You can set it up that all rulers of Twilight Realm would be Midna(just reincarnate her every time she dies) For Twilight Princess event, have it replaced with Zaant and up invasions.
Complete side topic.
I highly suggest you take a look at Hyrule Total War/Hyrule Conquest for some inspiration.
Hyruleconquest.fandom.com
ThatOneOldtaku
joined
This member has provided no bio about themself...