I didn't even notice that. Well spotted. That definitely gives NRS the freedom to change Scarecrow up.
As for your theory, it sounds completely plausible, but it doesn't make sense for Ra's to be absent from the roster if he plays such a pivotal role. Unless he is operating purely from the shadows and not directly involved.
I believe Ra's might be the teaser at the end.
Revealing he was the one pulling the strings, to hype the sequel.