what goes around comes around
There are two separate issues here, one using seniority for promotion and the second is using seniority for pay and benefits.
The AC situation is an inevitable consequence of a pay system that shafts the people at the bottom for the benefit of those above. This is consistent feature of union environments. (Might also explain unions losing power all over)
The AC list makes it so dammed good at the top that people are going to fight to stay. The AC pilots can fix this by going to a rotating bid system, something totally inside the realm of their contract and ensuring that joe senior gets to watch for sleighs every few years. Pay can be based on time in service. (note - that is not age, but time in)
Seniority for pay and promotions is a managers dream for two reasons. One is it solves a vexing and expensive problem, scheduling. The best part is it ties pilots to the company like nothing else.
The argument about seniority for promotions might have had its merits at one time but all sorts of industries deal with this without such a remedy. Command upgrades still require assessment and evaluation. The insurance companies and the regulators are going to be very interested in how this gets done. Also any real company is going to have written procedures in place and will follow them or spend years in court fighting discrimination cases. Again seniority based upgrades does management a favor as it saves them from actually having to develop policies and implement them. At the end of the day they are going to train X pilots and they better mostly pass so its only upside to the company to have the selection done for them.
I can see why people on the inside working their way up a long list are invested in the current system but overall it screws pilots like no other group I can think of. The sooner the whole thing is dumped the better. It seems Mr Ennis might be the poster boy for change. A "fair" roster at AC would benefit the majority of the pilots. Yes there will be no more glory days of being #1, but even in the old days that never lasted that long anyways. OTOH if you presented a deal to the current pilots that said:
1 - from now on you will get Xmas or NewYears at home for half of your remaining time at AC, if that is what you want
2 -your pay will still progress as under the current system
3 - The new system will give the fly till you die crowd a real incentive to leave (Not that it matters anymore)
I suspect you'd get a buy in from the majority.