Focusing on low cost carriers is probably a good move, but Southwest and others are going to be very reluctant to come to GSP until there is a second runway. I think the majority of the effort should be spent on adding additional cities such as Boston (Delta), Miami (American), Denver (United/Frontier), Phoenix (US Air), LA (pretty much any airline), Austin, and San Francisco (United). Direct international flights seem very unlikely, especially to China since I don't know if GSP can accommodate those planes. Maybe start with Toronto or somewhere in Mexico? After adding routes, if they can't land a low-cost carrier, the committee should focus on getting multiple carriers on the same routes to try to drive the prices down with the existing comptetition.
RDU is a good comparison for an airport that is maybe 15 years ahead of GSP.