But if it can't function as an airport, its shops won't be used. Instead, the tills in the shops in DXB, CDG, FRA, AMS etc. will jingling away. But as retail (who buys luggage airside?) is considered to be part if the deal, the remote terminal complexes will solve that issue. Furthermore, as extortionate airport rentals won't have to be paid, other attractions could be bolted on to the terminals to make them attractive and sexy places to be in their own right. That can't be said for Heathrow. I'm sure I saw a sign near the exit in C4 that said "Please wipe your feet."
Heathrow has to increase its capacity to thrive but it's location means that is not possible. Therefore, start again but quickly. The clock started ticking 20 years ago.