It's a nice idea but even a non-technical person like me can think of a few snags:
The 'pallet' would be a huge thing, and very heavy. In order to be able to load it into the aircraft shell, it would need to be rigid, and therefore rather heavy. If such a size of pallet were feasible, then I suspect modern freighters would use them in order to reduce loading times.
The 'quick release wings' (already commented on) would have to be very quick indeed to be quicker than pumping fuel in. I think I'd prefer permanently attached ones myself.
The majority of pax would rather ride out an emergency with the crew than be ditched in the Atlantic in an aluminium box, I think. Those parachutes would also be a lot of weight to haul around the World.
Assuming the off-going crew get out quickly, the departing crew only have about 10 mins to check the aircraft, programme the FMS, and depart. That's not a lot of time for an aircraft that's just had its wings changed!