I think it is necessary for there to be a button in the pre-battle popup screen that allows for changing formation prior to the battle start instead of just only having the option to fight or retreat… This way it does not slow the game down and I no longer need to police my surroundings so much so I can pause to change formations before engaging another party on the map.
I also think that being allowed to change weapons before battle starts is also fair, since the company moves along with the cargo wagons, no changing of armor though!