One of the greatest economic developers and supporters you can have is an international aviation hub. Dubai became not only an airport with people connecting but also the main economic centre of The Gulf, despite having hardly any oil. If it wasn't for connecting passengers Dubai would still be back with a few buildings around The Creek and a scatter of flights. Frankfurt managed to develop as the German financial centre and international business location, despite having by no means the largest population or economic base. It was a pretty small place 30 years ago.
Heathrow is excellently-placed to serve as an East-West hub connecting Transatlantic traffic with points East, a role which it already serves admirably within existing constraints. However, it is not geographically well-placed to serve as an all-points-of-the-compass hub. Dubai is. Frankfurt is. Istanbul is. Munich is. But London isn't. Look at the map. Britain lies on the western periphery of Europe, great as an Atlantic airbridge, not so good for intra-European transfers (amongst others). London stands to lose much of its connecting business as new long-haul flights are introduced direct to cities across Europe and beyond, regardless of whether LHR's physical infrastructure is expanded or not. Passengers will prefer the growing selection of non-stop flights from their own local airports, or the simpler routings these new services may offer where a change is still required.
The prime concern now must be to develop a London Airports system designed to serve
demand inherent to the SE, both business and leisure derived. An incremental hub role is a luxury aspiration which London should not pursue in the light of the extraordinary costs quoted to make it happen. The cost is not justified by the potential reward. Even the CEO of British Airways - LHR's largest hub operator by far - argues against the project on the grounds of cost.
Contrasting LHR with DXB / FRA as a hub choice is not a valid comparison. Apples and oranges. And before Skipness points it out, let me be quite clear. Neither is Manchester or any other UK airport! MAN can serve as a hub at the margins - in a niche-role linking FlyBe-type destinations with the wider world, for example - but not as an all-points-of-the-compass mega-hub. Dubai it isn't. Dubai it can never be. Neither MAN nor LHR. Geography mitigates against the UK in this. That's a fact of life.