Roman line relief

[Robert Vermaat]

Was there ever some sort of rank switching during battles between sections or centuries that the Romans used? Like a passage of lines?

I can only answer that for the later Roman period in which it was extremely unlikely, given that the army took care to have the front rankers armoured if there wasn't enough for all to go around.
There's also a theory that the so-called 'antesignani' were soldiers who fought in the front ranks, protecting the officers and standard bearers who also led from the front, both of which would also make line relief difficult.

But I'm hardly an expert in such matters.