I should preface this by saying that this idea came to me before even watching the film. Once it was announced that an action figure of Joseph Gordon-Levitt's character CGPD Officer John Blake would be released, I wondered what a custom turning it into Robin would be like. Alas, I have not acquired this figure yet, so for this conceptual look at a "what if" scenario where John Blake somehow becomes Nightwing/Robin (won't discuss how that's addressed in the movie, it's not as entirely straightforward as one might think), I used the head from a Marvel Ghost Rider movie Blackheart, with the front of the hair shaved down, the face painted over and a mask sculpted on to. I couldn't find the right neck pegs so this was a royal pain to attach to the Survival Suit Bruce Wayne body. The details are sculpted on, and went for a mix of the blue colour scheme with a dark, rust-red since the New 52 Nightwing has a suit with red highlights. The escrima sticks are from an old DCSH Nightwing, with the handles cut off.
UPDATED with the actual John Blake head. I was hesitant to use the John Blake head as I only have one and it's hard to find, so I came up with a removable mask so the head can still be placed back on the policeman body. The mask was made with a twisty tie and a piece of soft card.