Look the only way we can legally make airlines to use the Thames Hub airport (THA) is to close all other airports in the area, if we just close LHR, then BA and others would spend huge amounts of money buying up slots at LGW (because it is more conveniant to use that airport than the THA), if you close both LHR and LGW, then the same will happen, only it will be both Luton and Stansted
Hence why the THA would be a white elephant even if only some of Londons other airports would remain open
That's absolute nonsense. Do you really think the other London airports have the capacity to absorb more than a small proportion of Heathrow's traffic (even assuming that carriers such as BA would want to move flights from a hub to a non-hub) ?
Also I don't think 6 runways are enough (you would need 8, most of all when you are dealing with all of Londons air traffic)
That's predicated on your previous assertion, and is therefore nonsense too.