While I'm certain I could not have put all that into words, I do and did understand it. But that doesn't mean that I agree with it. You see, I don't believe that there is right and wrong, at least not ones that are so obvious and clear cut. And I believe that even if Carl has strayed from the "right" path, he is hardly an "ultimate loose cannon," as you called him.
If what you say is true, then Carl's character underwent a transformation somewhere in the second half of the season, away from the boy that saved Tyreese and his group, that gave Michonne a chance, and recognized Rick's failures. Away from that, and toward what? A boy that suddenly believes his father's way of doing things, pushing people away, and generally being "hard" is the solution? I don't buy it. That's too rapid a change with too little warning. From my perspective, Carl this season hasn't been an impetuous boy railing against authorities and adults for failing to give him more leeway and responsibility. I see him as being among the brightest and best of the prison group, someone that could very well be one of their top fighters and protectors, if not for his age. And he recognized it, and it stung, and yet he did his duties despite that, making him all the more impressive. So I fundamentally disagree with your assessment of the scene where Carl shot the kid. If you don't approach it with the perspective that Carl is hungry for power or for an outlet for his frustration, then you're left with two choices. Either Carl did it because he's sadistic and evil, a position I don't think anyone could support, or he did it because he felt threatened. Perhaps it was merely just instinct, and Carl has learned to trust his instincts after months of living on the verge of death. Whatever the case, I'm willing to have faith in him, certainly more than in Herschel or Rick.
But those are just my opinions based on my understanding of the characters. You'll no doubt be proven right because you take into account the structure and nature of the show, and how such stories are told in general. But I don't like Chekhov's guns, and I don't like characters whose arcs exist solely to reflect on another character. If that's what happens, hopefully the Walking Dead will be able to fool me into believing that there is a natural and logical progression to this, because I find thinking in the terms you described to make things hopelessly dull and pointless. I'd much rather Carl find his own way and be dealt with in a manner entirely unrelated to Rick, while his father deals with the increasing pressures and challenges of leading a larger group. Surely those problems will merit some character development for him as well.
