The magnificent game developer responsible for the Smash Bros series (among other things) was interviewed about Brawl four months after its release date. However, this interview appeared in Nintendo Dream, a Japanese publication. To my knowledge, this is the first time the interview was translated. Let me repeat that, this interview is old!
Anyway, there was one particular series of questions about Wolf's inclusion in Brawl over Krystal. It really gives an interesting behind-the-scenes look at how they had to make their decisions about which characters to include. I've quoted the relevant portions below.
Question: Why did Wolf become a playable fighter, and not Krystal?
Sakurai: Wolf was a character that barely made it in due to time constraints. He was added because there was high demand for his inclusion on places like "Smash Bros. Dojo!!", and he's a popular character. Of course, if he didn't have that backing him, I don't think I could have put him in. Among the characters with high popularity, I chose one who had a high possibility of becoming realized in the game, and as a result you could say Wolf was created.
Host: Does that mean even if you wanted to add more female characters, Krystal didn't have a realistic chance of being physically implemented into the game?
Sakurai: For Krystal, we didn't have any of the technical modeling knowledge that we had cultivated with Fox and Falco, so it was like making a brand-new character from scratch. And because of the limited amount of time we had, creating Krystal wasn't realistically possible. On that point, with Wolf we already have some knowledge of how to model his character, and would require about 70% of the effort required to create a whole new character.
Host: I see. But we did get a lot of questions like, "Why wasn't Krystal a playable character?"
Sakurai: It's not that I don't understand how that feels, but if you start saying that, it becomes "Why isn't Waddle Dee playable?" or Dry Bones, or Baby Peach. There'd be no end to it.
Host: Well, that is true (laughs).
Sakurai: In the end, the three playable characters in this game from "Star Fox" are Fox and Falco, and on top of that, Wolf, because he was popular and easy to create. On the other hand, if it was a situation where it wasn't easy to create this character, and we had to make him from scratch, "Star Fox" may not have had 3 representatives. So, please think of Wolf as a lucky inclusion.
Interpret that how you will, but at the very least, we know that...
- Krystal was considered for Brawl
- Wolf only barely made it into Brawl because he was popular and so similar to Fox and Falco as a fighter
- Had Krystal been in Brawl, she would have been a fighter very different from Fox, Falco, and Wolf
Source, thanks to thatveryweirdperson for the heads up.