So how do you propose a fair unbiased system that allows senior FOs to be promoted with no seniority in place?
Are you saying seniority based systems are fair and unbiased? They aren't always. prejudice and favour will creep into even the most rigorous system.
And what do I propose to replace it? Nothing! I have a great deal of seniority - therefore I'm for it. I was merely pointing out that it is becoming less important. Pilots with experience have greater mobility now. Pilot employment is controlled by market forces - and the market is changing. The common trend is changing to pilots paying for their training and rating with a LoCo, getting their command, getting some experience and then joining the charter market.