I would love to rewrite Broken as an original story that could be published. I still love the basic storyline and think it would work as an original; it would just need to be totally de-Backstreet-ized and trimmed down, and I know I could do a better job of writing it than I did the first time around. That said, I've had that goal for about 5 years now and still haven't made much progress on it LOL. I'm finding that it's a lot harder than it sounds to completely reimagine and rewrite a story.
Hannah had mentioned wanting to write Something Beautiful as an original, and I think that one would turn out really well. A similar story that would make a really good novel is The Market by Susan. Interestingly enough, in thinking of all my favorite fanfics, there aren't that many that I could see being translated well into original fiction because so many of the ones I read are very BSB-centered. I don't think they'd have the same magic without "the Backstreet Boys." Like I said in another thread, I think AUs work best, but I don't read many AUs.