I think some airfares allow stopovers ? I just think you would be carting around your luggage and checking in etc too much , if you have an indirect flight your luggage can be checked through to your final destination if they are the same carrier or in an alliance or have an interline agreement ? ( I think that's what it's called ) ?? Say you wanted to fly to BKK and did UK to AMS on easyjet and then flew with KLM to BKK , I think you would have to collect your luggage in Amsterdam and then checkin with KLM , unless they have an agreement .

On your example you would get a flight to Scotland and then have a separate booking 2 days later to fly long haul departing from there because it has a much cheaper or no APD ( if that happens !!! ) If that does happen it will cheaper to get an Emirates flight from there than other UK airports for example , also Etihad are starting flights from Scotland next year so I think it would be something people might do more often , and as they are fast expanding airlines the choices become more , it wouldn't just be if you wanted to fly to DXB or AUH , that could just be a step to fly onto the Far East or Australia and that would be a considerable saving on flying from LHR with the current UK APD charges . ( not that I'm advocating Scotland should vote yes !!! ) I'm sure there are more important issues !!