436 you observe correctly however some of the actions are also driven by safety considerations. No equipment shoud ever be placed on the a/c until it is chocked and the F/C confirm brakes are set to 'park'.
Easy always outsourced the 'GHA' and they were lucky to obtain the services of' Reed Aviation.
The arguement for outsourcing rumbles on one of the key points in having your own should be a better service? However, BA has a futher problem in that being large at the moment there are no companies big enough to take us on. If you commit to a GHA they service a number of airlines and may not give the best service due to divided loyalties and also promising far more than they can achieve. (dont we all).