^As I said I'm not sure it'd work unless the person travelling back is a future version of someone already close to the existing FC cast. Rachel Summers would be cool, but it'd require too much exposition and would probably necessitate (re)introducing Cyclops. Kitty wouldn't work because in the original story, she quantum leaped back into her own past self's body. The whole point being that the messenger was someone they already knew and..well...the movie version of Kitty won't be born for a few more decades.
Raven is probably the only one of the bunch who'd still be fighting fit 40-60 years in the future AND is already central to the plot of FC.