NEXT: Gen 6 starters get new abilities

Greninja justification: Flavor purposes, a ninja is sneaky and it allows other options for Greninja.
Delphox justification: Magic guard makes sense on a magician, allowing sash and LO to be better on Delphox.
Chesnaught justification: Large armor for flavor and better defenses. Not Shell Armor since Blastoise also gets Shell Armor as a NEXT ability.