Anyone would be foolish to doubt that U2 would not open a base at SOU in a heartbeat if the facilities were in place. SOU is perfectly placed to cater for the capacity that LGW and LHR do not have space for. BE simply charge too much to appeal to the masses, and in the affluent south it is not unusual for people to go on 4/5 holidays a year. U2 would do very well serving all the usual city break destinations and will have the bonus of also catering for cruise passengers (Southampton is the cruise capital of Northern Europe). As a previous poster has pointed out, a polish route would also be a good move. I believe Southampton is 1/8th polish and some of them will go as far as using Luton to fly home cheaply.
BOH invested 45m airside in an attempt to speculate to accumulate. It would be nice if SOU could invest at least half that to make the facilities available for U2 to make what will be an easy decision for them. I am not sure stands 1-5 could handle anything more than 2 A320 sized aircraft at one time. When an aircraft of that size is on those stands it takes up 2 stands. Stand 1 is also awkwardly set back so I believe cannot even handle a q400.