I am not sure if this has been done before in the comics, if not then it would be cool to be the first to try this with Batman villains!
The world would have to be an alternate universe story, and each villain would have origins that make use of two characters combined, but played out as a single character.
This is Selina Isley. Both loved and hated by Batman. She is not only a scientific genius in botany, she is also an incredible thief.