[steffandroid]

This is a pointless thought experiment that has practically no basis in reality.

[umvi]

I disagree. Unions tend to favor seniority-based promotion over merit-based promotion[0] for obvious reasons (unions can't tell how much merit an employee has without deferring judgment to company managers/execs, but unions can tell how long someone has been working without deferring judgment to anyone).

[0] https://www.jstor.org/stable/2523767