Whst about making Manchester a hub.
It has a huge investment from the Chinese.
I'm sure they coukd double the size.
It can be linked to HS2 if they start next year on HS2 and it's northern arms at the same time Eg Start HS2 In the North and South Simultaneously .
Give Manchester two more runways and new terminals.
Bring BA up lock stock and Barell .
Manchester like EMA is in the physical middle of the map.
In real terms its not too far from Most of England , Wales and Scotland.
Granted there woukd have to be serious investments and slits from Newquay and Exeter perhaps reopening Plymouth to give the Southwest equal accsess to it by means if regular feeder traffic
Heathrow can continue to be a large airport but if you had another UK hub mainly for the UK carriers it it would surely Free up LHR to a host of new routes and international carriers.
Perhaos even the likes of Ryanair with no bother of expansion .
I just dont see how continously expanding Heathrow is the answer.
It can't be.
Because sooner or later yiyr going to.run out of safe airspace