Originally Posted by Whiskey Tango
Nate Grey is an alternate universe Cable designed to cash in on Cable's popularity except he wouldn't have his powers limited by the techno organic virus. Like Cable needs his powers limited to stay interesting, otherwise nothing poses a threat to him anymore. Not only do we only need one version of Cable but we also don't need a character who's an incredibly powerful psychic with a connection to the phoenix force with no weaknesses. This is also taking into account that Cable will most likely be introduced in the same film and if Stryfe gets introduced at a later date, than that's THREE Cables running around.
Now even getting past the fact that he's an overpowered version of an existing character, Cable himself has the same powers as his mother. Granted, they have different personalities and different weaknesses so they both stand out and neither is a Mary Sue. Rachael Summers (who is both a female Cable and a younger Jean Grey) comes close to Sue territory since she has the control over the Phoenix Force that both Cable and Jean struggle with but she avoids being a true sue by having a nasty temper and having her psychic powers be slightly weaker than both Cable and Jean to compensate for stronger Phoenix powers.
This brings the total to FIVE Jean Greys (the other four of which have more to offer in terms of plots and character development than X-Man does) running around with one just being a carbon copy who can kill most villains with a single thought, has full control over the Phoenix Force and lacks any true weaknesses. I'd rather see somebody like Maggot, Forearm or Nurse Annie than have X-Man appear. He's a horrible character and is best left forgotten.