That reminds me of a theory i toyed around with a few years back when I was thinking about writing fan fiction. it basically had the Phoenix force being created as the result of Jean's powers manifesting with her friend's death, but it was too much power in such a young girl, so her mind fractured and the fragments scattered across space and time . I think I was going to include Jean having latent chronoskimming powers like Rachel to explain how the fragments traveled through time.