The point is that it'd be a little gross to hinge a lot of appeal on the diversity of the cast and turn around and open votes on alternate sexy versions of your female characters. You inherently harm the validity of these characters as anything other than eye-candy, and you lose out on protection when it's not even the artist's 'call'.Umm
Alright, it sounds like the guest characters are going to be a lot more optional than the rest of the cast, but would a more sexualized err say Toko drive away people? More than it'd potentially bring in a choice your favorite design or something?
Still, respect to Lab Zero for doing what they want, not taking compromises from publishers or backers.