Well, the Strikers series, like all Mario sports titles, are separate from the real Mario canon. They're just fun sidegames that don't really have an impact on the true Mario storyline in any way. IMO, it's okay to have Mario and friends go out of character for the sake of a meaningless sports title. As long as the game, itself, is enjoyable, I'm fine. Besides, it would be kinda dumb if all the females in the Mario world were girly-girl all the time.
On that note, I really didn't like Peach's voice in Charged. She sounds too... teenage. I know it's meaningless sports game, but I think they could have done better. It's kinda funny, actually.