For one, as much as I love Bane in the film, Deathstroke would have been a much better fit. However, for the sake of this being a simple change, Bane’s still the villain. So, in the film, Bruce is in the pit for five months. They should’ve had him be in the pit for at least ten months. Why? Well, Bruce and Talia did the bat dance before he was in the pit. So, if he was in the pit for over nine months, that would be enough time for Bruce to (unknowingly) have a son, Damian. So, in a hypothetical DK4, a random league soldier charged with taking care of Damian would have left Gotham and trained the boy to become a deadly assassin. This solider would be Deathstroke, the new league leader. If Damian was 13/14 in the film, that would set it just ahead of our current time. So, the plot would be similar to Batman: The Brave and The Bold. Also, side note, did Alfred actually see Bruce, or was he just imagining it?