Someone like Zatanna could work. It would address the gender issue and give the League a magic user that it currently doesn't have. Plus I think Wraith's Batman has some form of relationship with Zatanna, so her being a member of the League could cause a nice tension between the two of them.
Either way, I don't want the League to be so OP that characters are redundant.
Either way, I don't want the League to be so OP that characters are redundant.