One area that could improve the speed of getting off the plane is the gate checked baggage pickup passenger queue.

The passenger line waiting for gate checked luggage is normally inside the narrow jetway. This line starts on one side of the jetway. The 2nd person who joines the line waiting for a bag lines up behind the 1st person. 3rd behind 2nd. As this line of people gets longer some idiot decides they are more important then everyone else and starts their own personal line on the opposite side of the jetway. Then more people join this shorter line. Now the narrow jetway has a line of passengers on each side of the narrow jetway with other passengers still exiting the jet squeezing through the middle.

But...then it happens. Gate luggage starts arriving at the plane side of the jetway. Now you have the same narrow jetway, two lines of passengers waiting for luggage, one line of people leaving the plane just trying to get out and a person who spotted their gate checked luggage going against the direction of the only moving line trying to get back to the jet side of the jetway to get their gate checked luggage. ...then a 2nd piece of gate checked luggage appears, ...then a 3rd...

In my opinion, this is the bottleneck.