Possible theory for an origin of _ in the mcu (BND spoilers)

I think Sarah’s Death might have created Phoenix.

In the books it was her dying friend who was hit by a car then Jean trying to block her pain using her powers for the first time and the rage of that injustice that manifested Phoenix inside of Jean, then getting locked away by Charles and festering inside making it worse and worse.

I think the mcu might use Sarah for this, specifically I think the fact that Sarah’s mind reached Jean as she died is going to leave a part of Sarah’s rage at the point of her death in Jean as her friend did. AND I also think then instead of Charles it’s Sarah, the good part of her psyche, keeping dark phoenix blocked until something happens to break that, such as Jean about to die or in danger forcing Sarah to let go. We see Sarah set up as a protective figure with her blocking Jean from hopping to protect her from Damage control and it’ll be revealed she’s continuing to do that by blocking dark phoenix from emerging until she can’t anymore.