(Urban or High Fantasy) "Notes From the Investigator/Notes to the Undertaker" and "Secret National Occult Partnership Program"

So i'd like for both of these ideas to leave plenty of room for input and creativity, and I would even be open to a completely different premise if you want, lol. Ultimately, I wanna write letters as fantasy characters and encourage our creativity together.

For the first ideas, the basis is that both of our characters work for a company or coalition dedicated to studying all aspects of supernatural creatures. One of our characters could be a traveling investigator studying the behavior and patterns of these creatures, and the other could be an undertaker or ecologist responding with the findings and details about the species. One one end, I imagine letters consisting of vivid descriptions of beasts and cities and people, reviews of local hostels and restaurants, and developing monster mythologies to follow up on local stories. On the other end, I can see lots of pseudo-scientific notes and details about monster physiology and history, interesting and unconventional tools for dissection or analysis, and even possibly some complaints of the clerical aspects haha.

With the second idea, i imagine that we're both members of some sort of program that unites magic practitioners with each other for advising. This one is a little more open ended, but my thought is that maybe one of us could be a newbie and the other could be more experienced, or maybe we're both new and learning together. I imagine a lot of trading recipes for potions or refining instructions for spells, details of interactions with villages and which places are accepting of witches and which are more of the Salem types, and of course updates and doodles of our familiars! Anything honestly, this prompt strikes me as more of a diary share than a narrative with chronology.

Of course, it goes without saying, but no matter the premise my main interest is in developing two characters within their own unique world, and getting to build a dynamic between them. And both of these premises are open to suggestion and subject to change, so if you have any ideas i'm happy for us to implement whatever! If this sounds like fun to you please feel free to let me know!