There is a lot of talk here of all the disadvantages at SOU and why that means the airport cannot be the success that many hope for. IMO focusing on the negatives will get you precisely nowhere.
Look at LCY. How long a list of disadvantages do you need? Runway, obstacles, crosswinds, often visibility issues when there is little wind, special training, limited aircraft, limited operational hours, no certainty of future political support, you could go on and on. It has of course one huge advantage and that is why airlines find a way of operating from there despite everything.
OK the knockers will scoff. SOU is hardly LCY
they will cry out and that is true but you build on what you have going for you and it not the case that the airport is without its own advantages.