i like the concept, especially since night-wing is currently batman, and will return to being night-wing, it seems like it would be a hybrid of the batman design and his original night wing.i really feel bad suggesting things because it is an original design, and like art, its part of the artist. it's like saying the Mona Lisa would look better if the background had more blue. but since you asked i hope you don't mind...
1) i personally prefer the original bird/suit color scheme, instead of the inverse that you went for. just a personal preference
2) i would move the bird up so that the whole design ends in his torso and have it go over the deltoids. it feels weird having his symbol/logo over his stomach. imagine if the Superman S, or the bat, or the green lantern symbol was over the stomach/crotch.
3) i think the helmet idea is very cool, but not practical as is. the helmet is meant for protection, but you sacrifice vision and range of motion. a cowl/mask is great for moving, looking, but no protection. this is a helmet, but with a open mouth, so it compromises the helmet. like a fort with open door. i think a better idea would be if the helmet can close. either the top part flips down, or if you want to keep the "beak", have the edges of top and bottom piece actually touch (does this make sense?)
4) i think i like the cape of your original drawing better. but i like the split in this one, but this one looks like the wings of an insect instead of bird. I think you should still keep the wing shape so that it does the same effect of the bat with batman
5) in general, i say pick 2 colors, and create the whole thing with it (
maybe a third if it is black or white). i feel that there are too many different colors.
--this isn't a design idea, more of just the drawing. NW is kinda small compared to the mugger. if you look at NW's feet the are kinda small compared to the guy's face, or even the guys own feet. it looks like a robin. if you can, try to make the character bigger with photoshop or something
i hope you don't mind. again, these are my personal suggestions, not flaws.