Very interesting.
There is a story, "A Different Shade of Black", I believe, where Narcissa Malfoy raises Harry, after Bellatrix sacrifices herself to save him.
I would be interested in seeing where this Harry ends up... and how his childhood with Bellatrix as his "mother" will go.
Of course, I also recall another story where Bellatrix was friends with Lily Evans/Potter, and founded to bare Voldemort an heir, to "spite" him, Bellatrix goes to Lily for help, who comes up with a spell to combine the two children... thus "Harry" has two mothers and two fathers, one of whom was a mind-controlled Bellatrix, whom he released by cursing her.
Author's response
Sounds pretty interesting, I'll have to hunt that story down. I remember reading the other, though I can't recall if I actually liked it or not.