Ok, WTM, you've got a bite!
The problem with Direct Entry Captains into BA is that there are enough qualified people there at the moment waiting for the "Dead Man's Shoes". Not saying this isn't the case anywhere else though.
We took some direct entry captains a few years ago with the take over of CityFlyer. As the CityFlyer aircraft were dispersed elsewhere, a deal was done to ensure that the CityFlyer captains kept their commands, even though they were bottom of the seniority list, with certain restrictions. One of which was if they left LGW shorthaul, they lost their commands, as they were about 1500 places short of holding a command at LHR.
If we were to recruit direct entry captains, a similar deal would have to be done no doubt, and these people would almost certainly have to go to the 'unpopular fleet' at LGW as the popular vacancies (basically anything at LHR) could be covered by suitably qualified current employees. Therefore there would be unlikely to be any movement off the 'unpopular fleets'.
Keep in mind that any DE Captain would have to be paid the market rate for the job (otherwise he or she wouldn't come) so it's actually to BA's benefit to recruit to the bottom of the pile and promote from within. Think about it, an experienced BA co-pilot who has many years of operations under his belt is well paid as a co-pilot. By promoting him, the wage bill to pay him as a captain and then recruit a new junior FO to replace him is likely to be less than to keep paying him a high FO's salary and some new guy as a Captain on broadly the same pay. Also, this would result in a lot of experienced people jumping ship as they were 'passed over' which would cause the overall experience level to decrease on the flight deck and insurance premiums to increase.
I'm sure if BA thought it was in their interests to advertise for DE Captains, they would have done already.
Just my opinion though.