Eh, just make him Scott and Jean's son from the future. And only elude to it, don't make it the central point. Skip the whole Sinister/Goblin Queen/Apocolypse/Askani/Stryfe storyline.
Problem is, Cable's entire backstory is entrenched in X-Men mythology. You seperate that from him and he's basically just a psychic cyborg with a gun.
That's true, but you can keep the whole Commando Jesus sent back in time to prevent the rise of En Sabah Nur while ditching that very complex origin tale.