I know that the aircraft is tail heavy on the ground with the body gear not extended but how much of a risk is there for a tip over in a normal configuration with a normal expected deplaning procedure.
It's probably a good idea to have someone monitoring the attitude of the aircraft whenever you have non-standard disembarkation or cargo unloading. Normally, on larger/longer-bodied aircraft, passenger disembarkation will be at the front of the aircraft via aerobridges with automatic level (height) adjusters (and aural warnings if the door hits the sensor placed under the open door). If passengers disembark at the rear, it will normally be via mobile steps which may not have automatic level control. Therefore, large shifts in CG can either make passenger embarkation/disembarkation difficult or damage the doors.
I've seen, on occasion, full pax version 744s almost reach full nose strut extension when too much cargo has been removed from the forward hold (from an arriving aircraft with not much fuel on board). If memory serves me correctly, the 744 electric cargo loading/unloading system will be disabled if the nose goes into "air mode" (just prior to nose actually lifting from the ground). This should at least slow down the unloading, leading to less chance of a full tilt (and hopefully make the cargo loaders run to the nearest engineer to ask them for guidance). On the other hand, passenger disembarkation is only impeded by airplane to aerobridge step size
