While I'm not a huge fan of the Anime, I've found Mallow and Lana to be the bright spots. While I feel Mallow has the most potential of the two, she's been relegated to the background for the most part despite yielding "Leadership" qualities since the first Episode. She's also had several dramatic Episodes, notably Episode 108 that easily ranks as my #1 SuMo Episode. Lana, on the other hand, has the potential to surpass even Kiawe as the best battler of the Alolan group besides Ash. Her calm and cool demeanor under pressure would easily help her in competitions like Coordinator Contests and with a performer Pokemon like Primarina, she could easily dazzle in Pokemon Showcases.
If either character were to continue on in another series, either of those characters I would enjoy seeing more of.