Main_Tenant
the main issue with 380 is not runway length but taxiway width and wing overhang. Obviously Robin Hood were able to design in A380 from the start where older airports have to adapt.
As for diversions: remember one engine out of four is a lot easier to choose diversion than one engine out of two, and makes losing an engine on takeoff easier to manage! A short ferry flight to origin/mx base or to destination will reduce TOW well below the usual requirements. 777s have been popping into tight fields too - people manage to sort them!
(edited for clarity)