After the terminal development has been completed it will be a ton of taxi fuel instead of 600kg as the queue to cross 23R and at the 23L threshold will be even longer at 7am in the morning.
Manchester made a big error when the 2nd runway was built to close for true dual use operations. But that is so typical of the UK, transport development is so often half hearted and does not look far enough into the future. The 3rd Runway at Heathrow needs better transport links if it is to serve a large part of the Country, not only road's but HS2 needs to call at the airport and connect with HS1 at St Pancras/Kings Cross giving access to the Midlands and East of England as well as a direct link for trains from Reading and the West to call on the way into the Paddington.
But Manchester is no better, some of the express trains from Crewe and further South should be diverted to serve the airport as well, along with a link to North Wales.
Unfortunately, or perhaps fortunately this Country is London biased. If we live outside of the South East then we are 2nd class citizens but at least the illegal immigrants do not know of nor wish to come to the Midland shires.
British Airways are also equally London biased, in Germany Lufthansa operate long hall from both Frankfurt and Munich. BA could have developed longhaul from Manchester in the 90's/00's but they lacked real foresight and retreated to Heathrow instead.