Seniority should never be looked at as a stand alone issue. In any airline worth working for you need a seniority list with associated rules on how you get onto it. Then there is the Ops Manual Part A, B and D covering all the SOPs, training and checking procedures so everything is transparent from the outset of how you get to the LHS. Then you need decent and independent training and checking departments, a bidding system with associated rules on who gets a shot at the title and an ombudsman to oversee any issues that might arise and need adjudication.
Its not perfect but I would rather that than the short term view of DECs, threats of base closures, bidding for your command and naming a price that goes on in certain bottom feeders.