You have fundamentally not understood how the market behaves. You cannot make LHR better by taking what it does best elsewhere. Gatwick has been tried as a hub, understand why that, with arguably better facilities in the 90s and noughties failed, and you'll learn a lot.
You are re-regulating a market and so you will need to select winners in those who stay at LHR and losers, those whom you move to Essex. Each one would be illegal under the free market and Open Skies agreement and even if it weren't you would then have to favour one operator over another. Again, open to legal challenge. This is not the 1970s and Macavity Brown is no longer in No 10.
Take NYC-LON. Who decides who stays and goes? How do you decide?