I think it'd be pretty tough to get a plane's worth of bags from the hold to anything resembling an orderly display within 120 seconds of the first person getting off the flight. Let's assume that the collection location needs to be at least twice the wingspan of the plane. That's 400 feet for a 787, or 140 feet for a 737. There's a benefit to consistency at a given site, so let's stick with the 400-foot number. That's 90 seconds right there at typical walking speed (3 mph). So, to meet the SLA, we'd probably need to open up the entire hold, length-wise, rather than pulling out bags from one or two doors. I'm not an aeronautical engineer, but designing a door into the length of the fuselage seems like it could be on the same order of complexity as designing a plane for supersonic travel.

Meanwhile in the real world you have the automated baggage system that they attempted to install in Denver.

http://calleam.com/WTPF/?page_id=2086

In what theory? How would you actually go about accomplishing this? I'm sure the airlines would very much like to know how to unload a full plane's worth of cargo in 2 minutes.

they actually built systems for this but it has never been implemented. Basically you make the cargo hold completely removable from the plane. There is a box that slides in and out of the bottom of the plane. Someone just drives up with a fork lift style vehicle pops off the container and takes it inside the terminal where it can be dumped out onto the conveyor belt. I am surprised they have not automated the entire baggage system. It seems like it would be feasible to automate just about everything. You know where the plane is going to park every single time just fix that position and have something under it which can directly attach to the plane and pull the bags off and conveyor them under the ground and into the terminal and it can auto sort the bags to the right destination. It would not be easy to build but it is doable and would remove the need of large percentage of workers in the airport

Perhaps this would require bomb-bay doors on the bottom of the hold?

With small planes it basically works like this - on many of the tiny regional turboprops, your baggage is waiting by the side of the tarmac as you exit the airplane, and you pick it up before you enter the terminal, not at baggage claim.

It's mostly a problem of scale. Unloading 20 bags in the 5 minutes or so before the passengers start to deplane is no problem. Unloading 500 bags would be.