They're not going to make up a new goal for a female lead that doesn't exist in the games. At least you can say Serena's goal was loosely based on the ORAS Contests which is why they didn't start in the anime until after ORAS came out in 2014. The anime is intended to advertise the games, so unless they just have a female Gym leader, the girl does a game-oriented quest. I don't see them doing another Misty/Iris type character anytime soon, and so far S/M has no new announced sidequests.
As I said before, they can actually pull off a Pokémon Racer now. S/M seems to be featuring lots of rideable Pokémon so we can have a companion whose goal revolves around that.