Your premise is that quantum gravity has effects near the singularity and that the event horizons is a barrier to getting information our from within the horizon.
So a simple theoretical investigation is to look at a very very small black hole, one where the outside of the event horizon is still near the singularity and thus the quantum gravity effects are visible because they are happening outside the event horizon.
But if you don't have good experimental or observational data about small black holes (and if Hawking radiation exists such small black holes don't last long so are constantly changing) then you can't use this to test your theories.
And there are other approaches as well, approaches where spacetime is emergent and so the event horizon (like all of spacetime in such a theory) is just an approximation to something else.
If you are talking about theories that make predictions about situations we haven't been able to test and can't figure out how to test then the door is wide open. Its not wide enough for a layperson to just make up any theory whatsoever because it still has to agree with known results (which have very many particular details to get right) in regions where results have been tested. But there are many possibilities.