So I wanted to make this thread to suggest a system that you can link to the unending codex that has been implemented in this patch (6.1).
The idea of this is to either have it as a job, or a system like the sightseeing log that's already in the game. I would personally say something like the sightseeing log is good, that way you can have the rewards based on the achievements you go through.
The point of this system is to learn more about the civilizations in the game, primarily the older civilizations.
We have a lot of older cultures that we know about in the game, like the Nym, Amdapori, Ronkan, Meracydians and more, these are just without mentioning the obvious ones like the Ancients and Allagans.
You could integrate this into the unending codex you receive to learn more about each civilisations cultures as well as architecture and history, this incentivises the ones that really like to figure things out about the world of FFXIV, as well as gives rewards, that can be related to the civilisations we research about.
For example you could research the past of the Ronka to find out how their civilisation lived and how it developed over time, the reward could be that you were able to figure out how to replicate a piece of furniture, armour piece, or something else.
One example I can think of is of Amdapor, considering they used statues to create golems based on beings of light (maybe sin-eater adjacent?) we could maybe figure a way to recreate a golem based on their white magic.
If you did the system similarly to the sightseeing log it could be something that leads to the next clue, maybe something like the broom quest in matoya's cave, it just hints to where the next piece might be, or an idea where you would look.
This could also be used earlier in the game than endwalker, but I think this would fit since we're going to go back to adventure, and exploring lost civilisations, ruins, and more certainly gives me adventure vibes ^^
Feel free to respond to this to add your two cents, it's always great to have a discussion ^^