A Central Scotland Airport in Falkirk (Skinflats area by Grangemouth) was indeed planned in the mid 90s, but never got any further than the 'planning' stage.
It would benefit Scotland, and make life easier for passengers and airlines - using one central airport, and I for one would be all for it, however cant see it happening anytime soon... Cost, politics and the length of time 'public consultations / enquiries' take, would totally finish the idea off...
BUT - look at the UAE and their take on tourism and jobs... They are building another airport in Dubai, as well as upgrading the existing one.
OK, ok they do have zillions to spend, but they are looking ahead and making facilities available...
We live in hope!