Looking forward to what could happen with the extension. Taking a simplistic view after looking at some takeoff performance data for the A320 Neo. At max takeoff weight required takeoff run is 1951 metre, with under 150 metres less than this available at SOU. Max range at max takeoff weight 3500 NM.
With TFS under 1600 NM from SOU, maybe an option? A lot of other prospective destinations close to or less than this.