Thats assuming that staffing is a fixed parameter, it's not (Stockholm syndrome).

If pbs were adjusted to better respect seniority, the company would have to hire a few more pilots. Oh well.

I'm not sure suggesting every requested day off needs to be granted, only that seniority is reflected as to who gets that day off. If a senior pilot creates a Chinese puzzle that pbs cannot solve that's on him. But if his last layer contains only a very specific bid, then no junior pilot should ever get that day off instead of the senior.