I’ve been on the hunt hoping to find a shot of James Earl Jones saying the words “Your Mother”. So far no luck, but he does say “Mother of God” clearly in The Hunt for Red October. I don’t know crap about audio editing, but Vader says “You’re feelings have now betrayed her too”. Wonder if those words can be strung together to make the line “You’re Mother once thought as you do,” without it sounding like the Joshua war computer form War Games.
Even if the proper words or dialogue spoken by him saying “your mother” were found, the voice would never match the tone, rhythm, and beat etc. with the way the full line is spoken during the scene.
Maybe using a James Earl Jones sound-alike?