RF,
I have only ever done super-long-haul once, and I understood all flights operated on similar lines. My route was FRA-DXB-BWN & BWN-BKK-DXB-LHR.
In both cases, we were taken out into the terminal, and iirc, back into different seats. So are you saying you stayed on board at BKK? I didn't think that was the way they did it.
Does an airline version of a 'cross city' service not 'sweat the assets' and keeps aircraft in the air for longer? Just a thought.
Not really. Even a long distance train will pass through certain stations which are effectively hubs and change crews, load the trolley etc. You are still suggesting a landing at DXB - so all those passengers from BHX would fan out to numerous places across Asia & beyond - why pick one? Utilisation wouldn't be that different, but a particular type would then be committed to two sectors instead of using different ones - for example, there is discussion above of bringing the A380 into BHX, which may suit certain timings - but the onward routes may be operated by anything from an A330 up.
There are numerous flights that operate with so-called 'fifth freedoms', and there are even treaties of 'cabotage' allowing foreign airlines to operate domestic flights within a different country - although I can't think of any flights ex UK that take advantage of that - EU Open Skies is a different step altogether.
There was a good thread a few weeks ago about EY taking a slice of AB, and the political issues that brought up.
Hope that gives you a few pointers, but there should be a fair few airline insiders here who can elaborate further.