Since they're using fixed/static and not component-made units, while I am probably in the minority on this, I hope they don't duplicate the weapon types over and over. Granted, it's probably more historically accurate, but then it would be even more accurate to simply have mixed unit weapon types, and that's bad for balance. While not necessarily bad for balance, I don't really see the point of three or four different types of units who all wield the same exact weapon whose only difference is attack/defense when you can increase that through experience or infrastructure buildings anyway. For instance, while both Ashigaru and Samurai wielded all different lengths of yari, I'd rather just have the ashigaru be pikemen and samurai be standard spearmen. Another example would be to give the iconic naginata to the sohei only and samurai something like a nagamaki instead (which was the favorite weapon of Oda Nobunaga).

Although I realize it's early to be thinking about mods, I nevertheless had some fun playing around with how I would probably do this and came up with something like:
Nagayari Ashigaru (nagayari/pike, light armor; spear wall formation ability)
Oyumi Ashigaru (oyumi/arbalest, wakizashi/shortsword, unarmored; plant stakes ability*)
Koyumi Ashigaru (kokyu/shortbow, wakizashi/shortsword, light armor; fire arrow ability)
Teppo Ashigaru (teppo/portugese arquebus, wakizashi/shortsword, unarmored; plant stakes ability*)
Taiho Ashigaru (taiho/cannon, wakizashi/shortsword, unarmored; small shot ability)
Tousekiki Ashigaru (tousekiki/catapult, wakizashi/shortsword, unarmored; flaming ammo ability)
Nagamaki Samurai (nagamaki/glaive, heavy armor; challenge/chant ability)
Odachi Samurai (odachi/greatsword, medium armor; challenge/chant ability)
Teyari Samurai (teyari/spear, heavy armor; spear wall formation ability)
Yumi Samurai (daikyu/longbow, medium armor, katana/longsword; fire arrow ability)
Waseiteppo Samurai (waseiteppo/japanese arquebus, katana/longsword, light armor; small shot ability)
Keikihei Samurai (horse mount**, odachi/greatsword, medium armor; wedge formation ability)
Juukihei Samurai (horse mount**, nagamaki/glaive, heavy armor; wedge formation ability)
Kyukihei Samurai (horse mount**, daikyu/longbow, katana/longsword, medium armor; circle shoot ability)
Soukihei Samurai (horse mount**, teyari/spear, heavy armor; wedge formation ability)
Ryuukihei Samurai (horse mount, waseiteppo/japanese arquebus, katana/longsword, light armor; circle shoot ability)
Naginata Sohei (naginata/halberd, light armor, portable shrine)
Kanabo Sohei (kanabo/spiked iron staff, unarmored, portable shrine)
Kyu Sohei (hankyu/halfbow, katana/longsword, unarmored, portable shrine)
Kihei Sohei (horse mount*, naginata/halberd, light armor, portable shrine)
*plantable during deployment only
**Juukihei Samurai become Nagamaki Samurai, Keikihei Samurai become Odachi Samurai, Kyukihei Samurai become Yumi Samurai, Soukihei Samurai become Teyari Samurai, Ryuukihei Samurai become Waseiteppo Samurai, and Kihei Sohei become Naginata Sohei when dismounted

...which is 20 total, rather than 30 or 40 as I'm not keen on "faction unique" units either. Better to just go STW1 way and have certain factions or provinces have an "honor" or income bonus on them. (BTW I realize the japanese is probably off in the above :-P )

Another thing I hope they do, which was related to my problems with "tech trees" in another thread that I posted in, is make the dojos train more than one or two units this time. This is slightly less of a problem with M2TW's recruitment system (haven't played the newer gunpowder ones) but I've always found it more a tedious pain in the arse to have to build a whole building for one or two types of units than strategic. In what I posted above I'd probably go with:
Sojutsu Dojo: Nagayari Ashigaru, Teyari Samurai, Soukihei Samurai*, Naginata Sohei**, Kihei Sohei*/**
Kenjutsu Dojo: Odachi Samurai, Nagamaki Samurai, Keikihei Samurai*, Juukihei Samurai*, Kanabo Sohei**
Kyujutsu Dojo: Oyumi Ashigaru, Koyumi Ashigaru, Yumi Samurai, Kyukihei Samurai*, Kyu Sohei**
Hojutsu Dojo: Teppo Ashigaru, Waseiteppo Samurai, Ryuukihei Samurai*, Taiho Ashigaru, Tousekiki Ashigaru
Bajutsu Dojo: *required for all kihei/cavalry
Butsu Tera: **required for all sohei/warrior-monks

Which is 6 buildings plus a castle for 20 unit types, rather than the original's 15 or 16 buildings for about 16 unit types plus different levels of castles. Upgrading the buildings/castles would just increase honor or something. It's silly you have to wait so long to access units (other than gunpowder) at the start of the game, especially one in this short of a time period. While on the subject of castles though, and only partially related to units, I do hope they bring back the originals maximum amount of units garrisoned in a castle per castle size, although I'm pretty certain they won't.