I just thought of a random who is Arkham Knight theory while looking at this picture of Oracle.
I'mma just copy and paste everything
I haven't read all of the post in this topic, so forgive me if this has been mentioned already, but while looking at the picture of Oracle I've come up with an interesting theory as to whom it may be.
So the picture I was looking at was the picture of Oracle that was zoomed in on, to show that she was wearing the Flying Grayson necklace. She could be wearing this because she is in a relationship with Nightwing, but that is too easy. What I think is that she is wearing it as a physical memory of him. Sometime between AC and AK, Nightwing may have gone missing, died (But not really), or anything.
So lets say he died. Ras is certainly getting revived from the Lazarus Pit and he could be furious with Batman that he let his daughter get killed and did nothing. So what would he do? He would revive Nightwing and condition him into the perfect enemy of Batman.
This would explain that he has no real origin, because Nightwing is presumed dead. Venezuela could be where they revived him in a Lazarus Pit and began training and funding him and his army. This would also explain why Rocksteady said that who he is doesn't matter, because it wasn't necessarily important because Nightwing was brainwashed and didn't up and decide "I hate Batman" one day and change his life forever.
I know this is a completely random theory, but it popped into my mind after looking at that Oracle picture for awhile.