A Nightwing movie would flop...at this point. General moviegoers do not know who he is.
Take the X-Men approach and center the movie around Nightwing the way they center the X-Men movies around Wolverine.
If its a hit then you can put Nightwing in his own movie. I think getting the right actor to play him is key as well a great script and developing Richard Grayson/Nightwing as an interesting character.
IMO, it should wholeheartedly be Tyler Hoechlin. The kid who played in Road to Perdition as Tom Hank's son.
He is 6'1" and 20 years old. When I first saw him and the movie, I thought it was the perfect model for a Batman and Robin movie and this kid is Robin.
See IMDB for recent pics. This is Richard Grayson!
http://www.imdb.com/gallery/granitz...00.jpg?path=pgallery&path_key=Hoechlin, Tyler