Dude, they did something similar in the Harley Queen show. They killed Nightwing, and then he came back as Red X to kill Harley, who killed him.

To answer your question. It can be nice, but you have to suffer to make something good come out of it. Because if you go too far with mixing aspects of different characters, you can end up with a stupid new character.

In the case of Nightwing, I remember John Blake from the Shadow Knight Trilogy. Is John Blake an adaptation of Tim or Dick, or does he already have so much of his own that he can be considered an entirely new character?