All of the characters you listed are excellent supporting characters, but would never function well as stand-alone protagonists. All of the companions in the game are designed with the Origin System in mind, meaning any of them must be not only a companion, but also a stand-alone protagonist. This approach seems to restrict the avenues they can take each companion, given they are not only companions, but also competing protagonists. Add that to the fact that we only have a very limited amount of options, and there just isn't space for what you're talking about, given the direction of the game and its inspirations. I agree with you, but I think Larian is aware of the problem, but just see it as something to be sacrificed before the altar of their predetermined vision.
in my view, companions can never be the protagonist, because the companions are not the player character, they are npcs.
the companions might have their own legends, but they don't have the destiny, and even they are not a candidate of the destiny.
the destiny of BG3 only can be decided by the player character, and depending on the player character's decisions that can bring on some of the companions' legends finally or strangle some of the companions' legends in the midway.
