Let's not forget that the BAI can't handle ambushes by sniping units. Sniping units stay hidden while firing and the supid BAI simply ignores it. Not good, CA!
Yari = Spear
Nagae Yari = Pike
Yumi -> Hankyu = Shortbow, Daikyu = Longbow
It is possible to specify how tight the men stand together, but I don't know if this has an impact on fighting efficiency.
In Shogun 2, yari are simple 1vs1 weapons, but CA got nagae yaris right. A pike wall is deadly. The front is nearly impenetrable and pikes do have a reach bonus. This allows them to stop charging infantry and cavalry. My tercos pikemen have slaughtered quite some units without sustaining any casualties, but the BAI was also very passive.
Still, for Boshin Realism, pike warfare is quite irrelevant as they are shot to death before they can encounter melee combat. Maybe a tight formation does have some effects ingame, as bullets would be more likely to hit the target. Too bad there isn't a shooting range in the game to test projectile stats.