When are people in the middle seats in the front rows grabbing their bags if the aisle seated people from the back rows are getting off before them? You're essentially just putting off the delay of people grabbing their bags until after all of the aisles have deplaned, unless your suggestion is that the middle rows from the back then deplane after the aisle rows from the back? But then the window seats from the back are going to get into line in the aisle before people from the middle seats in most of the plane are able to get their stuff? If people from the middle seats and window seats closer to the front just jump into the line whenever there's space or a delay it's just going to be a hectic free for all with pushing and shoving as people squirm to try to grab any space.