Or Heathrow's T5B, T5C - replace some of the walking with waiting for an underground train.
Yeah...but.....arrive at T5 on to an off pier stand (I.e. one where you are carried by buses from the aircraft to a drop off point about 100 metres from immigration/main flight connections) and you’ll hear howls of anguish and grumbles from those who would rather walk through the terminal complex than wait on board for something with wheels.....
I suspect this is one of those ‘you can’t please all of the people’ topics..
(there might also be issues with increasing the amount of vehicular traffic around the apron, investment in bespoke kit, etc..)