Its not really my area but offloading took much longer when positive reconciliation was originally introduced. As long as you know which container a bag is in it should be relatively quick to unload a bag although sod's law states that a bag will be in the first container to be loaded so five others will need to be unloaded to get at it. How long would it take the offload the first bag put into the bulk hold at the rear? I doubt it would be any quicker.
However you raise a question I have been thinking about for a few weeks. Might it be quicker to have bags assembled in some form of order in front of the handlers, particularly at an airport such as AMS with a lot of transfer traffic. As a passengers boarding pass is scanned a message is passed down to the ramp and the bag is located and loaded, early ones into containers and the last few into the bulk hold. If someone is delayed their bag will not have been loaded so the flight can still go and not miss its slot.
Obviously this won't work if someone on board has a panic attack but you can't cope with every eventuality. There would be an additional handling cost but it would save on delays. I don't know if anyone has done the figures.
On another issue, its interesting that the US does not require reconciliation for domestic flights (which I forgot when I was voluntarily bumped a few years ago). They claim that bags are screened in any case. Is positive bag reconciliation still valid given that:
1. Since 9/11 it appears that hardened terrorists don't seem to mind being blown up
2. Baggage screening has improved
3. There is an awful lot of freight on most widebodied flights (which has hopefully been well screened.
Views welcome on both thoughts.