Now im just throwing out an idea to you all that could either just strrictly be visual, or have some gameplay effect in it.
When infantry charged whoever still really had a reloaded weapon usually would fire it off while charging toward the enemy. Why not think of adding that into IG? mabye with a group of 60 men charging 3-4 of them would fire off their muskets at different times (to keep the individual soldier feel) while in full charge or in the whole chaos of fighting.
It would either take down 0 to 1 enemy out of the 3-4 that fire before they clash. I think it would look rather cool to see the smoke trails of the single rifles going off before the two lines clash. Or even when there fighting youd hear a rifle or two fire off in the first 5-10 seconds of clashing and see a small puff of smoke in the big pit of melee or something
What do you think?