What is wrong with it is - although I disagree with seniority lists - that FOs in BA may be waiting up to 15 years for commands in the present organisation. The labour force logically does not want to become a stale part of the organisation that will surely grow rapidly outside London if OS is a success. The labour force therefore want access to that growth for their future - which includes command opportunity and the chance to work outside London for a while.
Something along the lines of what I wrote a hundred or so posts back, along with the associated cost I mentioned.