Oh wow, I do really like that idea. One alternative scenario I envision is Tim Allen confronting the director, the camera panning to the new actor who ends up being actually older than Tim Allen's character. "You're not actually casting a younger hipper cast, are you?" "Nope, meet your character's future self. We're going bolder with older."
Or camera pans and he we hear him say, "Dad? What are you doing here?"
Then going with your idea, the younger original cast would end up saving the day...
