To me this is just a bit strange the whole argument of seniority lists. As far as I am concerned, and this is just my opinion, they are fantastic in the airline business. I quite agree that in other areas of business they do not suit or work but for those of us in the airline business they are a reassuring and comforting thing to achieve.
The airlines are constantly changing and with that comes a lot of uncertainty the idea of a seniority list helps promote loyalty, builds platforms for future growth and provide reward. As someone has already pointed out seniority does not guarantee a better position or financial gain as there are constant assessments and challenges to face in the aim of bettering oneself. They are however there to provide those the opportunity to do those things. It is all well and good to talk about the extremes of position i.e. the 10000hr Capt and the 250hr First Officer but think of all those in the middle. There have been many threads on the supposed experience perception based on hours. Those adamant that more hours equals more experience blah blah but as we pilots all know, yes hours give you experience but it is also based on far more that just flight time: Take-offs, Landings, variety of destinations, hand flying experience and weather but to name a few.
A seniority based system provides large companies with an entry level on which to build and it is then presumed that throughout your time at the company you will gain the experience that is required to take on the next step. Let us not forget that all those in these companies have had to pass a selection process to be there and so are expected to be of a certain competence already.
Seniority systems and T and C's are not indicatively linked but more the work forces representation by union and their own voice. A strong union presence helps control the attempts to degrade T&C's but the industry is significantly harder now than it has been and negotiations have to be made and agreements reached.
Each business is unique and I don't think it is really appropriate to compare the medical, financial and legal world with each other or aviation. As for the heading PILOT SHORTAGE where is that then? Certainly not in the UK. Maybe in the Far East or Middle East but culture then plays a significant part in a companies structure and that is a whole other discussion.
Like I said just my opinion.