The DCCU seems to be getting off the ground finally, and what better character to bring to the silver screen than Nightwing. The dark tone fits this character perfectly. I know most will say you have to make him Robin and establish him in a Batman movie first. I will admit that sounds fine but you can have a different approach that can work as well.
The route I feel would be successful is to have Nightwing, inspired by Batman to fight injustice. Bludhaven being the major setting of the movie. Blockbuster aka Roland Desmond had Dick Greyson's parents killed because they refused to be another victim of his extortion scheme. Blockbuster took over organized crime in the city. Nightwing was bounced from foster home to foster home, but trains his body and mind before taking the fight to the criminal element of Bludhaven. He sets up shop in Blüdhaven, becoming its protector. Inspired by Batman he became Nightwing to fight corruption.
Detective Soames and Chief Redhorn are two corrupt cops that work for Blockbuster. In his civilian identity of Dick Grayson, Nightwing joined the force himself and fought the corruption from within. Yet, while he may share methods and motivation of Batman, Dick knows what being Batman can do. He doesn’t want to become as dark, controlling and end up as lonely as Bruce. So with for all the good he may accomplish while avoiding it, one question is unavoidable—without going as far as Batman, can Nightwing be as effective as he ultimately wants to be?
The dark tone and the element of realism that is being implemented can lead to a great trilogy. The material that is there to be used gets me hyped wanting a Nightwing movie even more. I have said it before, WB/DC are sitting on a gold mine of characters that could be good on the silver screen. Its a no brainer considering the action, drama, and suspense a character like this can bring. If a cinematic universe is what WB is truly trying to accomplish, then Nightwing is a great addition to that universe. The same elements that make Batman so popular are some of the same elements that can make Nightwing just as popular.
This can set up the Nightwing character to team up with Batman in a future cross over film. Also you can have a Batman/Catwoman type relationship with Nightwing and The Huntress. Also if you wanted to introduced other characters such as The Question, Wildcat, Steel, or even John Constetine.
The possibilities are almost endless, so why wouldn't you pull the trigger and try it out. Marvel is confident and not afraid to pull the trigger considering they are actually going to do a Ant-Man movie. So in closing if Ant-Man can get a movie; why not Nightwing?