Why shall we not switch chars during set? Im sorry but if i know i suck at playing for example inf i play some other class same goes for my members....
I believe Sandorra just explained why the rule was made in the first place:
The player swapping has been on the table pretty much since the beginning. Originally, the point of the rule was to avoid delays on rounds and to prevent players from swapping class each round. Since Mercenaries has permanent equipment, this could be abused to quickly swap between fully-equipped archer, cavalry, shielder, and whatnot. It removes any semblance of tactics if the teams have completely different class-buildup every round, and then there's always that chance of rounds being played with players lacking and people shouting for restarts. Which leads us to the rule
And Ryzen, there are a bit more characters you can switch between in merc than there are in native. I have 8 different fully equipped characters that can most certainly destroy the opposition's tactics within one round. But as long as we both agree that swapping is allowed (or not allowed) no one has an obvious advantage and we're all good.
If someone took the time to change the rules a bit it would be easy though to write "standard rules" and we're good to go.