[Coldsaturn]

"I didn't think of champagne corks even once"
I burst out laughing. Caleb's EN VA, please make those kisses a little moist!

I like your recursive plot where the end of our present timeline triggers the beginning of an ancient myth like the Niava one! The fact that "the computer" told Zayne that our current timeline is not the right one broke me a little though. I'm seriously hoping we're playing the route that goes toward a happy ending, but I have this nagging thought that all the romantic cards we have that go past the main story calendar are a future we'll never get to see ourselves because we'll blow up before that.

Yeah they do know of one another (or at least, some LIs know of some other LIs, but they don't know them as love rivals; Raf is the only one I think that explicitly says "there's still time to care for someone else" to give MC an out), and I do believe they are actively influencing each other by influencing EVER. In the myths the others don't seem to exist, that's for sure, except for those that take place in the present timeline. The game is certainly doing an odd mesh of universes by insistently not going the poly route while at the same time not separating the LIs' paths in a clear way. It was already bad before in the main story, but at least they tried to separate the branches as much as they could. You'll see in D&R how bad it will get (to the point that there was some fandom infighting).
That being said, I LOVE putting them all together in a single timeline. And so long as playing with that option doesn't confuse you (since the plot is already confusing enough on its own), you have my full support and blessing.

The pantheon hierarchy is a bit complicated because a lot of it is very Chinese and what's not traditional to their culture is a melting pot of everything else they could think of. For example, there was a lot of talk about Foreseer Zayne and the localization choice of calling him a demi-god, which implies he is below the full god Astra. And what about Master of Fate? Is he a God god? Or is he a Master, divinity in status compared to normal humans, but still not up there with full-fledged gods? God of Annihilation in charge of killing worlds sounds divine enough, but then when Zayne is in his "Divine Tower" he explains that in that world those who had mastered the laws of the universe were considered gods. Which would imply that knowledge could make one ascend to "godhood" no matter his birth. So is he a god above gods, or is he a master of the laws of the universe, thus able to appear as a god to those who don't know those laws?
I do tend to approach the LaDS pantheon as similar to the Greek one (just to name one I am fairly familiar with). Each god might represent a different facet of reality, and this reality might be the entire reality for the single timeline we see them in, or just one possible out of many, allowing for the coexistence of more gods.

"he's more of an avatar of the Deep, is he not?"
We would have to say the same for Zayne, though. He is a god of annihilation in this myth, a demigod working under another god (unless we consider the theory Astra=Zayne) in another, in MoF he's not even the only one doing the job if we consider the old man. You're missing a few details about the Fractal Library from the WU, but we can already see that in Foreseer Zayne was in charge of it, and in this myth we see another man working as admin. If it's a single "power" related to fate we're talking about, it's passing through different people.

There is talk in the fandom that all the guys might be some form of primordial divinity, and of course we can then speculate that they're all supposed to be one single entity which has been split in 5 because of space-time mumbo jumbo.

/stops talking and realizes she's the only one in the room