I too have often thought about this topic.
Over the years, I have played different roles in my family. I have mostly been the scapegoat, but there was a couple years in there were I felt like the family hero. It was nice for awhile, but during that time I felt like I was pulled into the dysfunction of my family of origin even more. My mother would always compare my sister, my brother, and me. She would never talk directly to any of us if she was upset about something. In my family, we would always hear things second hand. For example, "You really upset Mom when you did X." Didn't realize how crazy this actually was until I started therapy.
I have sort of come to my own conclusion that the "roles" in a dysfunctional family are sort of randomly assigned. It's like having a play where you need certain people to fulfill different needs. Rescuers needs a victims and families that are not able to truly addressing their own problems needs a scapegoat to blame everything on. It helped me to look at it this way. It doesn't feel as personal any longer.
I once read that the only way "out" of a dysfunctional family system is through the role of scapegoat. This definitely happened to me when I started therapy/recovery. I was getting healthier, but since I was changing the dynamic of the system, my family thought I was crazy, a trouble maker, selfish, ... the list goes on and on.
I just chose to disengage and they eventually lost interest in me. At least I think they did, they could still be talking about me behind my back, but there's absolutely nothing I can do about that :-)
Thanks for bringing up the topic and for letting me share.
db