It wont happen.. they've tried this before..maybe..late 80s or early 90s?
You have to change how PI is enforced, not change the rule. Changing it to 15 yards max you will just have safeties knocking down players in the end zone all the time, have corner backs tackling receivers 2 yards past the line of scrimmage when they know they are already beat..because 15 yards is obviously better than not just a TD, but a 16 yard gain.
You just have to stop letting offenses use PI as a bail out play. Only call it on high percentage type plays, not every play. Basically, for all the rule changes that have made scoring more common.. there is finally some push back that it has gone too far and you need to acknowledge the defender has a right to the ball and that not every touch is "interference".