I think that Leonard Susskind's holography, George Chapline's "dark energy star," the Emil Mottola and Pawel Mazur's "Gravastar," the Polchinski's "firewall," and the recent ideas of nonsingular black holes clearly suggest possibility of understanding this phenomenon as a massive spherical shell with an asymptotically thin wall.
I think that whole mass of the black hole can be located on the same place of the surface that today we call events horizon.
What could prevent the collapse of this shell, is the hypothesis that gravity has a limit of intensity. This limit only happens in the event horizon.
I imagine that the intensity of gravity should not be infinite. If this is possible, then black holes have no content, because inside them there would be no gravitational field, no space, no time. A place that does not really exist. A contour region of our universe.
Can a black hole be a spherical shell?