Running two airports instead of one will only increase costs. You're just increasing the number of staff needed to be paid for the SAME number of flights. so same income, more outgoings, with air carriers failing left right and centre competition will just push more of those out of the business, leaving a few key carriers, who can ditact prices anyway despite the airports competing on the tax price side of things. Basically you need a minimum number of staff, on duty at ALL times, one airport at 100% capacity or as close as, or two airports, two of that set of staff, and both operating at 60% capacity. Utterly stupid idea.
how many people are on there, security, air traffic controllers, baggage people, etc, and all the emergency services that have to be on constant standby for immediate deployment. Then theres all the effort concentrated on a single area by police in terms of preventing terrorist plots and having patrols constantly around and so on, double the effort going on in the local area from that point of view.
2 massive airports on that scale simply wouldn't work. Its a massive undertaking but frankly, thats life, change is needed, simply making do because its what we have and because it will be difficult isn't a valid reason for not making needed changes.
You also have to remember, theres a lot of land there, a LOT of money can be made developing that land, a hell of a lot of money.
Not the same scale, but Arsenal spent £400-500mil moving to a bigger stadium, which now runs an awful lot smoother with far higher capacity, but they've made, hundreds of millions making flats in the old space
While of course you could keep all cargo stuff going to heathrow, frankly, cargo warehouses aren't the most complicated or expensive buildings to throw up fairly quickly. That will be one of the easiest things to sort out in terms of relocating.
It will hit the heathrow area very very hard though, hotels, housing prices will crash as its not got the transport benefit, though frankly most people pay more for a good link to get into the city rather than the airport. It should create essentially, just as many jobs as it would destroy just someone further over.
Its seems like the smart thing to do, just costly and will take time, and being that we live in England, massively over budget, late and the IT system will suck and need replacing soon after it gets turned on. But really, terminal 5 was hated by most, though it was needed, and the new link to heathrow was a waste of cash and time aswell. Its labours general thing though, why fix the problem, when you can patch it with expensive short lived useless things that no one wanted in the first place.