I have some problems with this idea.
First of all, like the comment above mentioned, if you impact the available designs based on what gender you're making for a character, you're giving the players less freedom to just create whatever feline or canine they want. Besides, having this would mean that when you enter a character creation screen, you'd first have to choose what gender you want your character to be before you can start creating it. And not everyone starts the design of their character with the idea of whether they want a male or female.
Aside from that, I'm all for being able to select a gender as long as it remains an opt-in sysytem, with a way to remove the male/female tag after picking one. I have a set of characters meant for exploring and messing around. Having a male or female tag to any one of those would be rather meaningless. So you're also gonna need an option to have no gender tag applied. This option would also be a life-saver if someone decides to try making a genderless character (like Entei, Raikou or Suicune from the Pokémon series) or in the rare occasion someone wants to make a character that is both male and female.