Greetings Gentlemen,
I've modded a while back for "Operation Flashpoint - American Civil War Mod" and would be interested in this mod as well - maybe some of the models could be used here? I also would recommend asking both the "1866" and the "Mount&Musket: Battalion" Mods for assistance or help, since they appear to have really good stuff going on that would definitely be a huge help for an American Civil War Mod. Maybe they would consider to lend a hand... - ...or even would let us borrow/use some of their stuff/code?
Also after looking around for a bit I recommend "movable formations" as this would, as far as I can se, do the trick to get AI to stay in a 2 rank battleline formation even when moving around: http://forums.taleworlds.com/index.php/topic,34685.585.html