Pay being an obvious one but again look to the current world systems for solutions.
But how many specialised jobs types are there in the world where hundreds if not thousands of people are employed by one of a small number of companies doing a nearly indential job?
I would speculate there are more transport category jet pilots than orthopedic surgeons for example.
There are more probably more accountants than pilots, but there are equally more accountancy firms than airlines.
If there was a transparent way to job hop then sure, but as non-seniorty appointments (TREs etc) prove, its wishful thinking that it will be entirely merit based.
Abandon rank, we aren't in the military, simply be named or designated senior pilot and pilot, it puts an end to chasing command
The problem is that command is where the money is, and I for one have no interest in taking additional responsibility for the operation if there is no additional compensation... and I doubt the airlines will put everyone through a command course to merely designate day by day who is senior pilot / pilot.
I dont doubt airlines would continue to operate perfectly fine without seniority, but what a pain in the a#$% it would be as a pilot trying to navigate your way to career-life balance as the invisible goal posts change (speaking from a non seniority experience).