I'm probably being dense here, but how can switching the packs back on at thrust reduction altitude cause an early retraction of flaps/slats???
Packs off T/O is SOP with us. It saves fuel - Pax want the cheapest fare; QED.
I didn't know about the pressure strengthening the fuselage, but surely at take off there is not much differential pressure, so this effect will be minimal near the ground?