Well, British Airways has always been recruiting Direct Entries onto B777 or B747 instead of promoting medium haul current FOs, does it sound great to you and Balpa? Would Air France and Lufthansa pilots allow that crap?
When you join BA you take a 5 year freeze on your initial fleet. You are not eligible to leave that fleet until your 5 year freeze is up. If BA have a requirement for 777/747 pilots (or any other fleet/seat for that matter), they always look to existing BA pilots first. They look at all pilots who have served their fleet freeze, and of those, they see who wants to move to the 777/747. If they get enough interest then all vacancies will be filled internally, probably resulting in some DEPs onto the shorthaul fleets that people have vacated.
This training year, there were not enough un-frozen internal bidders for the 747 - hence the DEPs onto the 747.
The system is perfectly fair, reasonable and transparent. By your logic, in times of heavy expansion/recruitment, people would joining and spending very short periods of time on their initial fleet and then moving to longhaul. The training costs would be astronomical, it simply wouldn't work.
When you join you are assigned a certain fleet (which you know of when offered the job). BA simply require that you spend 5 years on it before moving to another fleet. I have yet to meet someone who found that unreasonable.
I don't know what happens at Lufthansa of Air France, so I can't comment.