Well, the whole idea of the third runway is for Heathrow to further it's hub traffic. The airport needs to be effective in competing with the Middle East hubs, Istanbul, Amsterdam, Frankfurt and Paris CdG.
If BA were able to have a single London hub operation (moving Gatwick ops to Heathrow) and develop new routes to new destinations in USA, South America, India and China then Heathrow would become a more attractive proposition to hub through. Add to this more UK domestic destinations and frequencies.
Setting cost and regional ambitions aside I am afraid it is the Heathrow way or no way!