In my old group that was how we always played when there was more than one person per side, you would plan the tactics prior to start but once the game started you could not discuss the game. It does make one think about all contingencies and try to plan for it. It does make one pay attention to what your partner is doing. I had a lot of fun playing the game that way because me and my partner usually won over our opponents because our plan usually survived first contact.
I have seen rules before where you have to have a messenger get through (either in the form of an actual messenger figure, or just based on an arbitrary dice roll). If the messenger gets through, you can spent (say) 3 minutes discussing strategy, then it's back to the battle again until the next messenger shows up.