Okay, here's a first draft: https://wri.tt/43mbmsj9xj1eh7po
I guess some functions would require much more work than others, and most of them could be merged or divided depending on where you want to put the global specific/generic slider. Some of them are also possibly just plain dumb :) Overall it's a lot of cinematic stuff I don't really need for the game logic, but since my game is supposed to be rather atmospheric / contemplative, it's still important. I could add a few more features and ideas, but this is probably long enough for now :)
Let me know if you prefer using Workflowy or a forum post, since this isn't an editable/commentable document (yet, because it's a planned feature).
At the moment, I have designed a second map (very different and simple compared to the one you know), and my goal is to set up the beginning of the game, which implies to go back and forth between these two maps, one being the present and the other being the past. So I'll be able to test quickly all these enties and properties changes I mentionned earlier. And it's quite exciting!
Keep up the great work and cheers!