Seeing SOU is on a roll at the moment my wish list would be as follows.
Brussels Airlines to Brussels (possibly in cooperation with Flybe)
Easyjet to Geneva
Eurowings to Cologne, Stuttgart
Hop/Air France to Paris CDG
Lufthansa CityLine to Frankfurt
Swiss to Zurich
Volotea to Faro, Florence, Milan, Nice, Strasbourg, Venice
Vueling to Alicante, Barcelona (reinstated), Ibiza, Malaga
Plus both Thomas Cook and Thomson using their own aircraft on certain flights
Maybe I might be right on one of them!
Southampton Airport.......Build new stands, extend the taxiway and runway and they will come!