Here's my standard answer to that: we're looking for all types of victims. The only criteria, if you were to choose a character like any of the Robins, Barbara Gordon, or any character, for that matter, who eventually dons a costume for the side of good, you have to portray that character as pre-Robin, pre-Batgirl, or, in Dick Grayson's case, post-Robin & pre-Nightwing. I'm not one very enthusiastic about such characters, but that's my compromise for people who don't want to portray villains yet also don't want to be just some average Joe (or Jane) off the street.
I'd be more interested in having just your regular victims. I think that would give players more of an opportunity to create without having to work within the confines of a particular character.