Lol honestly I dont think its that deep. Oda isnt that multilayered and we are way too far in this arc to introduce this concept when nothing in the flashback hints at it. The most we've gotten so far is the Galleila and they likely are in Punk Hazard anyway
Imo the reason Heaven's realm exists is to connect the Adam and Eve trees together through Sky Islands (i.e. High West) and thats the only "layered" aspect I see here. Elbaf has Island Cloud, which very likely means its connected to Sky Islands in some way. Eve is allegedly the main Yarikiman Mangrove tree, which produces an atmosphere that allows bubble resin to form in Sabaody, Fishman Island and funny enough, Mariejoa as we see with the Red Line elevator and the floats given to the Mermen.
As a result, Eve is very likely near Mariejoa given what is stated in Fishman Island, and one way I can see Oda utilizing this is once Luffy becomes Pirate King, it can serve as a reliable way to get us to assault Mariejoa and Imu at that point.
We return to Elbaf (the only time Oda does this) and we use High West as a means to get back to Mariejoa without sailing backwards directly.
Anyway, its just a theory but I cant see Heaven's realm being any deeper than this personally.
To me, the more Oda hides something, the crazier the payoff is. I think the Giant Jack/Gods in Jaya will also tie back to Elbaph, along with Enel, who used "El Thor" as an attack, and is from Birka, which, in our world, was a Viking trading post.
I believe Elbaph used to have way more Sky Islands/clouds connected, but they separated during the Void Century war, due to the tree losing branches/general warfare.
The Straw Hats climbing up through Eve is interesting.
Do you think we'll go inside Elbaph's Adam Tree? I also wonder if there's life living in it. Possibly Tontatta, since we know the Giants/Tontatta mated in the past.
I want to know if Heaven World is forbidden to enter. If it is, it's important, and, Luffy's going there.