Best option for more stands would be to the north of the terminal around the corner where the ground training and carpark 3 are. There is room for at least 4 more stands for 737 size aircraft. ISTR there was a drawing for that when the new terminal was proposed.The security point for airside access could move to near the cargo shed.
Cargo shed I believe is listed as that is where Winston Churchill's aircraft was hangared., but it is only a T2 hangar and there are plenty of those around.
Back in the 1960s there was a proposal for a terminal where the main carpark is. It was to have a finger on the apron with north and south facing stands a bit like Gatwick in the early 60s..