Everything you described to me, and my own belief of a "timeline" theory, what you call "the electric charge of a Kerr black hole" aligns closely to what I call "state time".
The concept arises from asking what's at the center of any black hole? The answer people give is a singularity. What's that? It's a point where space closes in so much, there is no more room for anything else because the walls of the black hole press up against each other.
The other "part" of this (not part 2 of his field equations), is how do you and I measure time in our local universe? Most people will say they use a clock. So, how do you know how much time has gone by from looking at a clock? You do it by the physical displacement of the hour, minute, and second hands. If the battery in the clock died, and the hands stopped moving, and you watched only the clock, could you still tell how long you have been starring at it?
So, our way of measuring time is based on physical points in space, and not actually units of time. If I were to roll a ball across a table, the past would be the ball's position where it started - a physical place. The future would be the destination the ball is headed for (another physical place). The present is where the ball is right now along the path between the start and destination end points. So, let's call our particular way of measuring time in the physical universe "spatial time".
If this is true, how do you measure time inside the singularity? There is no space there to put a ball (or anything else) and roll it around. Yet, black holes change. They can grow, shrink, and spin. What is time other than a quantification of change? Well, you mentioned a changing charge of a Kerr black hole's electrical potential. What if we used that instead to measure time?
The concept is similar to the clock speed of the bus and cpu in a desktop computer. It measures fluctuations in energy levels rather than a displacement in space. We can measure time in the black hole the same way, by counting the fluctuations of its electrical charge. Let's call this "state time".
Now, suppose the ethereal singularity our universe came from in the big bang did not actually explode in a blaze of self destruction. Let's assume parts of it only EXPANDED, and the rest of it is still there today. If this happened, it means what expanded took everything with it, including its own state time. In the expansion, state time got stretched out into spatial time.
This means, state and spatial time are still interconnected. One is just the inflamed end of the other. They can be mapped to each other. What would that mapping look like? On one side, everything is just a measure of a current moment of state (without any past or future). But, it's attached to spatial locations of past, present, and future. Can we travel along these mappings and combine them in deferent ways to arrive at different spatial points in our physical universe?
The thing that wraps everything up and holds it together is where is the ethereal singularity in relation to our universe? Well, it is NOT inside our universe, it is somewhere outside of it. Our universe is inside new space that this singularity created. And, I am sure that this is bringing up haunting echos of the holographic principal for you, as you seem to work with ADS diagrams.
But, instead of going into those, PBS Space Time has a good YouTube video on cosmological natural selection that visually depicts the big bang process I described. In the animations, watch the center of the black hole where a point space appears and expands. That is the supperlatice behind the inner horizon in which our universe sits. That's how the singularity and the universe can still simultaneously exist.
The outer horizon of the holographic principle is actually the inner horizon of the Kerr black hole. It's like the model of inflation when you blow up a party balloon, draw galaxies on it, and keep blowing it up. The outer horizon is the balloon's nozzle where you blow air into it, not the surface where the galaxies are drawn.
pbs spacetime: blackhole doorway universes
View: https://m.youtube.com/watch?v=rFgpKlcpzNM