Jabird
Yes! on BA9 we were given the option of remaining on the plane if we wished or stretching our legs in the terminal building, airside (some went off to buy duty free stuff), but you had to take your personal possesions with you while on board security checks were carried out.
No such option at Barbados (and Antigua on previous flights - NB: being very disloyal to BHX here!) though. You were required to stay put on the aircraft whilst we waited for new passengers /crew.
Take you point about pax fanning out at DXB - but thought that this might be a marketing opportunity for Brum and less down-time for the equipment.