"But let's ask a simple question first. Why does Heathrow exist? The answer is simple, it is an airport. Everything else is ancillary. It is not a shopping centre, it is not a parking franchiser, it is not a food court but rapacious management appear only to focus on these elements"
unfortunately if it's run by a private company a pure airport doesn't make enough money to cover the running costs never mind any return on capital
If you run it as a Public service it is either a permanent drain on the taxpayer (think Prestwick) or you set the fees to the airlines and passengers so high it hits usage
That applies wherever you put the thing.