I fly to Gibraltar regularly and the airport is well used by people outside of Gibraltar as well. I know Malaga isn't too far but there are quite a lot of people I know use Gibraltar to fly to the western Parts of the Costa Del Sol, like Estepona. There are also a few people who probably use it for the south west part of Spain as well.
I don't think a National Airline would work, but tis year will be the most routes GIB has ever had, and I can also see routes from Ireland and Scandinavia working too.