I’m not in the airline industry but have worked in organisations where seniority was the 1st determinant for promotion and have also worked organisations that were (largely) merit based.
Neither is optimal.
Under both methods there will always be those who should have received advancement, and didn’t; and those who shouldn’t have received advancement, and did – despite the best efforts spent evaluating their capabilities.
Seniority sucks when people who are “adequate” for promotion are selected ahead of other, more capable people, due to that seniority e.g. I’m sure there would be a FOs who would be better captains than some already in that role, and some FOs who would more suited to still being SOs …
Perhaps the process should retain the current pre-requisites for ‘promotion’ (as noted by parabellum in #37), and include some form of "peer" assessment e.g. from captains flown with; check captains; Sim evaluators; etc?
Also, from a quick trawl around the ‘net, the seniority system may be open to legal challenge. It would appear that, in Canada at least, some seniority systems have been the subject of court action due their perceived discriminatory effect.
regards
layman