I stressed the importance and influence of culture earlier. Earthbenders are the least spiritual because their bending style is anchored in, well, earth. They're not meant to be astral. I feel like completely countering that without a valid reason isn't sufficient. Moreover, this phrasing:

"By some very strange twist of fate, Nicias, as a infant, was brought to Wan Shi Tons Library by a Knowledge seeker. Whether or not the knowledge seeker thought he was an object of value remains uncertain but nevertheless that’s what happened. Wan Shi Ton and the knowledge seekers raised him, and even trained him from scrolls that taught earthbending. However Wan Shi Ton found several uses for Nicias as he grew. In terms of food the knowledge seekers brought him food"

That's a really weak reasoning. There's no backstory, no real logic to it. It just happened. He's age twenty. Knowledge is pointless without application and practice. I don't care if he read a thousand scrolls, he probably hasn't mastered one form of earthbending, let alone more. So far, there is only one character I would allow the title of master, and that is the Firebending Dai Li girl. Even if he's not a master, learning all of this would just make him more diluted in the fundamentals.

I feel like there is this... element to this character. This element of "this is what I want, and it's here just 'cause." It's going to take more than that. Soudai is a character that I'm sure Marc poured tons of effort into, but I didn't allow him (yet) because I didn't feel like he was completely authentic to the setting. I would take from that notion.