"the joinable companions should be the focus o' developing the story o' a crpg. the companions can grow, and player choices can change the ways in which they grow, but the motivations and personality o' the joinables is not so dynamic as to hinder quality writing. the essential qualities o' the companions (and major npcs such as the game's Ultimate Bad Guy) is known qualities that a writer can use as a foundation for story development.
I would suggest that this can be detrimental to the narrative, if implemented wrong. While I agree that joinables need to have crisis points and visible growth, I think Dragon Age Inquisition proved how fixating on companions can lead to a weaker story.
Inquisition has great companions, and bioware spent a load of time building their importance to the PC, and there are many great moments where you feel connected to the companions: Dorian's meeting with his father, when all your companions get drunk together in the tavern...
however, the overall story of Inquisition is weak, and it lacks any of the great moments that really made Dragon Age Origins so wonderful. I may have written this already but:
In Origins, I chose whether or not to father a child infused with the power of an old god, whether to defile the ashes of the messiah character (Andraste), whether I would free the tormented soul of some dwarf trapped in a golem body, and whether or not to have sex with a desire demon inside the mind of a possessed child.
in Inquisition, I think there was pool that maybe I could corrupt?
point is- it seems like all the thought went into creating this vivid companions, which resulted in a fairly bland fantasy plot, that relied on a recycled villain, and an antagonistic force that was essentially just the blight by a different name.
while it's clear the companions need to function differently from POE, granting them more agency along the prime narrative, and also presenting your character with contrasting and affirming view points, it can't come at the expense of the story.
At least, that's what I think
Also, agree that Kreia was an excellent character, often overlooked