If you think about it 60 years since the last change effectively means since the Patch Report in 1961. Super Constellations were still operating and the military had Meteors, Vampires and Hawker Hunters and of course the V-force. ATC was provided by Joint Air Traffic Control Radar Units. Secondary radar was in its infancy and there was no ATC automation. There were more military aircraft and less civil aircraft than today. While there have been many incremental airspace structure changes, it would seem that a 'ground up' redesign would be a good exercise although implementing the changes could be difficult (as stated above). The main impetus for the redesign should be efficiency, Some exercises in continuous en-route climb and descents already carried out by NATS show significant fuel savings (and emissions reductions if that worries you). The EUROCONTROL FABs are slowly becoming Free Route Airspace at high level, so the lower airspace should be redesigned with that in mind. There are other ways of maintaining runway acceptance rates that could be more efficient than stacks at LHR.
So I think it is a worthwhile exercise but the goal should be safety and flight efficiency and not maintaining majority slot holder positions ;-)