You missed the point if these multi R/w airports can spring up in the desert without any discernible local traffic then so too could Boris Island. The problem is we are trying to make it face both ways. A true hub like Dxb feeds on itself hunreds of interconnecting flights with 95% transfer traffic.
London is now missing out to this traffic , people use Ams Cdg Fra etc as it's easier to interconnect.
Don't think so, the major difference is that each of the "desert" airports have a major carrier providing the hub functions: EK at DXB, EY at AUH, QR at DOH. Boris Island clearly will not have this.
BTW the desert "
multi R/w airports" have 2 rwys each.
Boris Island has more in common with YMX rather than DXB, AUH, DOH.
If the 3rd r/w is built there will be yet another terminal associated with it leading to yet more complexity. I am not sure this will make travelling through Lhr any easier
Another terminal with a third rwy will be effectively an annex of LHR-5 mainly for one world carriers currently in LHR-3, so it's not particularly complex, it will make things much easier.