I don't see the issue to be honest, maybe we just don't have the no-fuelling restriction. If there is a fire the cabin crew is there to evacuate the plane and in the absence of a flight crew the gate agent is the ground security coordinator (and is legally responsible).
If, in the very unfortunate case that the plane turns out to have a maintanence issue that requires deboarding (O2 service, for example) then things will not be really that much slower than if you hadn't boarded in the first place. At least everyone already has their stuff in the overheads.