Well, the proffessor's a woman, so why can't they make the rival that as well? Honestly, I've wanted a a girl rival that was like a cross between Cynthia (I know, not a rival.) and Silver, like a bitchy chick that is a little mysterious. And maybe she could have a more diverse team, like maybe she could have a dragon for once. I would also want her to have more to the story other than Barry had in DP, she could actually be a part of Team "X" or be its leader that turns over to the good side after you beat her, but she's still badass, or she could have more importance by some other means. I would also like it if you had more post final battle battles, and in a better place than the Pokemon League or the Survival Area, such as atop a mountain, or the place you beat her last time, or the place were you first met, or some random route. I would also like it if the day wasn't so specific and the time wasn't so early. Plus, I would like her to level up more rapidly, I still haven't gotten Barry to raise his team higher than the first phase.
Edit: Just realized, Maybe we could have a different rival for the different games. like a Bitchy chick for White, and maybe a Energetic Barry like girl for white, but with a personality like Abby's from NCIS. That would be funny XD