Weapons in Nippon
Katana
For the purposes of this specific Army Book, I'd adopt the Cathayan Longsword, as it's an off the shelf solution that actually gets the results you want, though at 3-4 points it's more expensive than a Great Weapon at 2 points, but these equipped units are meant to prevail in extended melees.
No-dachi
Great Weapon; probably faster in real life.Apparently, not for commoners.
Naginata
Halberd, definitely faster in real life. If the Katana was mythologized, the origins for this weapon are rather obscure. For some reason, it's associated with monks, and the Samurai caste, especially women, which may have been retconned at a later period so that that commoners don't seem to use it, which is why it's not listed as an option for Ashigaru.
Yari
It's a spear, and like all spears, it's a multi-purpose item. Cavalry can use it as a light lance, the Samurai on foot like to use it as their primary pole-arm, as do the Ashigaru,but here you run into the difficulty if you use it as a normal spear, or a longspear/pike. By the time we get to the mid-sixteenth century, it's clear it's length has been extended for the Ashigaru, by the Oda clan to European standards for pikes, while the rest were satisfied (or more likely because they're troops couldn't handle) to a compromise between the spear and the pike, something along the lines of what we would describe as the ash spear (ash spear, get the pun?). Since we're generalizing, we'd take the High Elven variant and just add two extra ranks to combat, instead of the usual one for spear equipped troops. That would mean giving an army wide rule that any spear equipped unit gets ASF and +1 strength when charged in front by cavalry and large critters. The Yari Ashigaru would get ASF in the first turn of combat against everyone else.
Daikyu
Everyone gets a longbow, let's assume industrialization makes this easier than hammering out a variety with arrow shafts of different lengths; going by O&G 8, I'd say this costs 3 points. Ninjas are always a problematic bunch, so they'll have to forego medium range weapons.
Teppo
The rules in the BRB for Handguns should be sufficient; I'd cost them at 4 points
Ninja Weapons
Endless combinations possible; however, in Shogun it comes down to grenades, Ninja-to (presumably), , but they're not mentionedmaybe another hand weapon and climbing claws. I'd give them shuriken, caltrops and throwing knives, but they're not mentioned.