One thing I find interesting is despite the reasonably well off catchment area there is only one route to Italy from SOU. Verona appears to be doing very well too having been increased from weekly in 2010-12 to 2x last year and it will be 3x this year. This has been helped by the various tour operators that sell seats/packages to Verona and Lake Garda.
The Palmair Italian routes from BOH always used to do well, and newmarket are also doing well from there with the limited number of flights/packages they offer. I guess the chances of additional Italian routes from SOU has been slimmed significantly by Flybe's decision to ditch the E195's in favour of the more efficient but underpowered E175's. Still, I would think the likes of FCO, MXP, NAP, PSA, VCE would be viable a few times per week, especially with the backing of a tour operator or two.
As for who could operate them Flybe might look at MXP/VCE as they are not much further than VRN. However I do wonder if Volotea would look into operating from SOU, as it seems to suit their business plan of operating 'secondary' european routes away from the major loco competition. They could also look at operating some of the sun routes which will be dropped from October.