Robbie Amell certainly has the look to portray Nightwing, and (at least compared to his cousin) he plays whimsical and charming better than he does dark and somber.
However, I think The Flash actor may be able to find redemption taking on an entirely new DC hero as Dick Grayson.
While Robbie Amell’s cousin Stephen has seen great success portraying the dark and brooding Oliver Queen on The CW’s Arrow, his take on Firestorm (and Deathstorm) has been somewhat hit or miss.
If DC wants a lighthearted Dick to counterbalance Bruce’s overwhelming darkness, then Mr. Amell seems like a perfect candidate for the job; all they need to do is swap out the Firestorm Matrix for a set of Escrima sticks and a domino mask.