Then we could assume that the interior of the black hole looks just like our universe, since our universe is smaller than its Schwarzschild radius. Basically we

Then we could assume that the interior of the black hole looks just like our universe, since our universe is smaller than its Schwarzschild radius. Basically we want to show that the interior space time of a black hole can be relatively flat. The problem to solve then is to calculate what happens at the edge of such a universe, and try to match that with what happens at the edge of a black hole, since those two would be the two sides. To unify that with QFT you'd have to include the particle collapse (or entanglement if you want to use the many worlds wording), where the quantum field would collapse to where the particle suddenly is inside the black hole instead of outside. I have long theorized that there is no way to unify the theories without using quantum collapses, so black holes could engulf particles via quantum field collapses only. The math for such collapses isn't fully established though, so it would need to have more theories on the quantum side as well. But at least that means nobody has developed a theory like this yet. The main calculation would be to calculate the probability of a particle collapsing into the black hole over time, by calculating how large part of the particle field is inside the critical area were it would be inside the new black hole radius. The particle and the black hole would get entangled for a bit where it is both inside and outside the black hole at the same time, and then the field collapses and it is fully inside. I think that can actually work! Then the black holes event horizon is a natural quantum effect, which could potentially provide the missing link between the two.