GLA is my old home town airport as well - and I must say after passing through it a few days ago and despite the new departure and security areas being forced through shops) I still think the airport looks tired....and empty! x2 easyjets and couple of Flybe, 2 globespan and a midland and BA Airbus.
An airport to serve the central belt would I also belive be of the benefit to Scotland.
The travel to and from such an airport is an interesting issue - however many new airports are build well away from centres of population and work very well. Look at Munich - moved from being nearly "down town" back in 1992 and has developed and progressed wonderfully to be consistently climbing up the airport useage charts year on year....yet has only 2 train (S Bahn) lines to the city centre which run every 10 minutes and can take over 50 minuts to reach the city centre. No one seems to be that bothered about such a journey.
Nivsy