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.