Excuse me if this was done before...
Since Serena's going to be Ash's new companion, what do you think of the concept of a female rival for Ash as others speculated she'd be? That is, his main one like Trip and Paul. And I don't mean just for XY just so we're clear.
Try to answer these three questions as your response:
Would the writers even consider such a thing and go through with it (maybe to test the waters)? Best Wishes showed there was a first time for everything.
How could they do it right? A stopped clock is right at least twice a day.
How could they do it wrong? Having traits of a Shonen Anime, there's obviously going to be some biased towards males with a TV executive's "boys like boys characters in main roles" mentaility.