Not quite what you asked for, but the closest I can find: http://www.fanfiction.net/s/9507205/1/The-Last-Archangel

"Supernatural/Avengers fusion. No one knows where angels go when they die, not even the archangels. And if one finds himself in a different universe after death? It's one thing to leave heaven purposefully, it's another to find that heaven isn't even there. And Gabriel is alone."

Basically, Gabriel falls like Anna did, and gets reborn as Tony Stark. I haven't read it, so that's really all that I know about it.