Fenrir the Ice Wolf@Fenrirtheicewo1
Bending was a martial art affected by one's spiritual understanding and body movements.
If they wanted Bolin to be a Lavabender they could've given him a whole arc going into his mothers Fire Nation culture to feel close to them and through training in their movements develop lava Bending after seeing their commonality with the movements from the Red lotus Lava bender.
Look into who He was Learn who he was and see the similarities between them (being mixed nations, lost of family) and creating a form of Rivalry/mentorship with him... giving more to a Red lotus member because besides Zaheer, they were all one note and lame.
And not only give weight to when Bolin learns to Lavabend, but make it feel earned.
Plus, going deep into the shows themes ot the elemental nations being united. You know, do something with the damn characters.
