What about Airport overload, imagine 4+ full pax 747's or even the A380 (one day) arriving at an airport all at once, the surge of pax would be incredible, it would cause caos, as it allready does. Its allready battle mode at heathrow/gatwick/manchester (definatly the latter) trying to get baggage.
And the wake, is there someway around that one, i.e fly in certain formation to create a perfect flight? Probs not!