This is an excellent point. On single aisle aircraft, almost always once the rows in front of you have collected their bags from the overhead, you can walk nonstop down the aisle to the exit door. This suggests that if there was some way for Pax to load and unload the bins more efficiently, turnaround times could be quickened. The only thing that I can think of is to limit carryons to one, and only one, item. That is, no personal item in addition to your carryon. Most of the delays I see in the aisle are because Pax are struggling to maneuver multiple items down the aisle, into the bin, etc. If they have only one item, then they have two hands to manipulate it -- not just one hand with the other dealing with their other item.