Still here, ill have a CS ready soon
So it's exactly like Killing Joke, the premise of that attack in Alan Moore's graphic novel was to "mess" with Gordon because he had not known Barbara was Batgirl. Of course this is my memory of the comic, and it's been years (and I have a notorious love/hate relationship) with it. Assuming the GM edits the timeline to suit your origin/ideas, I think it could work fairly okay. I think the only thing is Barbara probably would still be in the 25-30 range as having Barbara be 16 with Tim Drake older would just feel wrong to me.
My two cents.