STN has major capacity for growth mainly because the market chooses not to use it. Only the locos have made a go of it and even EZY have downsized. BE need to carry way more full fare business traffic to turn a profit than people think. They sit between EZY and T3 in that respect. By all means they could use STN, all that would happen is that EZY and GR would ramp up and steal the existing LGW market. There is little evidence to suggest the market would be loyal and troop to Essex, some might but BE would be carving a whole new niche for itself at an airport with lower yields but admittedly lower costs.