Easy jet
I have long maintained EZY are a perfect fit for SOU. It's easy to forget that they are as much about the businessman as they are about holidays in the sun. They would fit SOU perfectly but as someone has already said we would have to sacrifice frequency. Unfortunately SOU is doomed to to a future with BE or another likeminded low aspirational airline. The only plus point on the horizon is the BOH operation being wound up once the subsidies dry up.
It's a shame an invester like Stobart doesn't come along and make a go of SOU. Look at what they have done for a pointless airport like SEN. It has all the right ingredients for a successful airport and even some ace up it's sleeves like being based in the cruise capital of Northern Europe. Unfortunately it's owned by someone's pension fund as a vehicle to park some money. Without the stands and taxiways being built the bigger airlines won't be interested.