See, I see a Bishop solo movie that way perhaps, but not Cable. Cable’s solo movie, spinning out of X-Force where we get more revealed about the character, is much more Blade Runner in tone. Or maybe even Blade Runner meets Avatar, in terms of pure aesthetic. His future sees the High Lords of New Canaan as this ruling caste, and yes En Sabah Nur is one of them but I would not make him the focus of the film.
Nathan is of the Clan Askani, sworn enemies of the High Lords and Clan Akkaba, Nur’s fanatical cult followers. So this film would have a setting which is both sleek and futuristic urban, in terms of the world’s mega-cities which are ruled by the High Lords, and also oddly alien in the forested and rural parts of the world where the Clan Askani hide and train, moving around so that the High Lords and their agents, including the dreaded Clan Akkaba, cannot find them. Stryfe would be a big focus and probably the main villain, but his shock troops (transported by Zero) would include characters like Sinsear, who we only met briefly in the comics but who had potential to be a scary villain.
It could be a weird and sprawling epic that is really, really cool and different if done right.