Arokey
Well, this is the end for me, I liked that you didn't make Jaune the protagonist because that's very cliche and I wouldn't have bothered to read it lol, but putting the protagonist with cardin + oc new character is a big no for me. For me always an oc protagonist or somehow you get into the rwby team (for shenanigans puposes) due to an odd number of students or you stay solo in a solo team for the same reason
If he needs a good excuse for his growth, he can just tell them his semblance is Adaptation and Growth. He can “adapt” to use nearly any skill, gain any power through practice, etc. All he needs is time and effort. You can name it something else, but make it something related to time and effort to achieve growth.
You really shiuld have stick with the original setting instead of adding weirs usless rhings that distract frol thé plot and the characters... there is nothing really interesting so far. Ylu protag got too strong too fqst so you have to détail and had way too much but again RWBY is à show based on its characters they are what make it interesting