As RHATO has already linked past canon into present I was thinking of past stories that could be used. Mime was...well a mime that hated sound. She was an attempt to create a Harley Quinn like character before Harley was around. I'd like to see her obsession with silence played up more, it'd be fun to have a mostly "silent" issue. But the problem would come from making her different enough from Harley and Jokers' daughter.
Who else could make a comeback from the Robin years?