On December 6th, 2013 I wrote an article covering all the teaser, and this was my original speculations for "Ollie is not the first vigilante":
"Now I firmly believe that Batman will never make and appearance in Arrowverse, but I don't think they will be shy about using [other] members of the Bat family. So my first thought is Nightwing/Robin. When I look back at the first season, they made references to both Central city and Bludhaven. Who is the first hero or villain that comes to your mind when you think of these cities? Central city: The Flash. Bludhaven: Nightwing. The teasers in the first season of Arrow could be setting up these heroes, since we know The Flash will be debuting soon(which we already have Barry Allen)."
To this day, I still believe it is Nightwing, given the reasons above, and new reasons. Steven R McQueen confirmed that he definitely talked to Arrow producers about playing the part of Nightwing and there is still suppose to be a name drop to a Billionaire from Gotham City. Like said in my original speculation, I do not believe they will ever use Batman on the show, but would use other members of the Bat Family. I believe that they will change up the source material, and make Dick Grayson the Billionaire from Gotham, who spends his nights fighting crime as Nightwing. Well, doesn't that contradict your Central city/Bludhaven theory? Yes and no. If my new theory is right, yes the old theory no longer holds weight, but while filming the first season, if they were planning on setting up Nightwing for this season, they probably didn't even know how they'd do it, so they made a reference to Bludhaven, not knowing they would end up making him a Gotham Billionaire.
So what do you think? Let me know below!