Restoring the red line will just open another can of worms, unless the other changes to the neutral zone are also reversed.
When they opened the game (supposedly) eliminating the 2 line pass, they also shortened the neutral zone by moving the blue line 2 ft closer to center ice**. They have also changed the faceoff positions. With the 2 line pass, the faceoff position was where the pass originated, but they have since changed the rules regarding the position of the faceoffs.
What would they do now..? According to today\‘s game logic a faceoff caused by a 2 line pass would be deep in the zone (faceoff circle right next to the net).
**At the same time, they moved the goal line back 2 ft. Increasing the defensive zone by 4 ft and making it nearly impossible to defend the points on the power play. This is one of the main reasons most teams best defense on the penalty kill is to collapse into the slot and try to block shots.