In the period of the list, Ashigaru used a yari up to 19ft long, which would rightly be classed as a pike. However yari came in various lengths from around 6ft upwards and I have not seen evidence of the longest ones being used by cavalry, so it remains a spear in their hands as far as I am concerned.
The naginata was used far more in battle in this period than the sword and indeed I have seen it stated that samurai were carrying lighter swords-more a badge of status than a battlefield weapon. Consequently it is classed as a normal sword in the list.
I accept the Naginata was used by the Samurai, but this is not an option for them to take; I would be happy for them to have that option to.
I also think they should also have the option for the longer two handed swords both on foot and horse back, this is based on lots of images of swords worn on the back.
It would be fitting to give the options of Halbard (Naginata or Sword) to all the periods for the Japanese and Samurai Armies and the 2 Handed weapon from 1331, the middle period onwards.
Hope this helps.
one source is
https://swordencyclopedia.com/samurai-swords/ which seems quite detailed, Osprey books also back up some of the details.
The website also includes some detail on the metallurgy as well.
"History of the Samurai Swords
The long history of samurai swords can be classified into Japanese sword eras—Koto, Shinto, Shinshinto, and Gendaito. However, dates may vary in different sources since Japanese historical periods do not match Western calendar years.
Koto Era
Japanese swords that came during the mid-Heian period through the end of the Momoyama period are considered koto or old swords. The Koto era is also known as the Old Sword period.
In the Heian Period (794 – 1185)
During the mid-Heian period, the Japanese swordsmiths had improved steelworking techniques, so the swords also developed curvature. The Heian warriors using these blades fought from horseback, and a curved blade was more efficient in slashing than a straight one. Swords of this period are called tachi, worn slung from the waist with the edge facing down.
In the Kamakura Period (1192 – 1333)
From 1192 to 1333, feudalism was firmly established in Japan. The samurai class had a strong demand for swords, which led to the production of better, more functional swords. Some of the main events of the Kamakura period were the Mongol invasions, between 1274 and 1281, which strongly influenced sword designs.
Sword designs included the addition of a soft steel core and more complex hamon, which made samurai swords more efficient. Swordsmiths also began carving grooves and horimono talismans to imbue protective qualities to the blades. The tachi blades also became wider, thicker, and heavier, requiring two hands to use. Many smiths also produced tanto daggers for close-quarters combat.
In the Nanbokucho Period (1331 – 1392)
During this period, five major sword making traditions, the Gokaden, developed in Japan. The Bizen school was the most active, while others were the Soshu, Yamato, Yamashiro, and Mino. Most samurai swords belong to one of these schools or of their offshoots. The samurai also used extremely long swords called odachi or nodachi and fought on foot rather than on horseback.
In the Muromachi Period (1338 – 1573)
It was customary to carry swords in the tachi style, slung from the belt with the edge facing down. Towards the beginning of the Muromachi period, a few low-rank samurai habitually wore their swords edge up into their belts. Eventually, it became a trend adopted by high-rank samurai.
Within the period emerged the Sengoku period, a time of constant civil war in Japan. There was a huge demand for swords, which resulted in mass-produced blades of lower quality. The uchigatana emerged for fighting indoors, as it could be wielded with one hand and was much lighter than the tachi.
The wearing of the uchigatana edge-up allowed drawing and slashing actions in one stroke, contrary to the two motions needed when the samurai carried the tachi edge-down. Also, the mounting hardware of the tachi was too bulky for daily use, especially when not wearing armor.
In the Momoyama Period (1574 – 1600)
In 1588, chief military commander Toyotomi Hideyoshi confiscated swords from all non-samurai. During this period, sword mountings became very elaborate and expensive. The uchigatana of the period were either mounted for combat or ornately mounted for gifts to higher-ranking warriors.
Shinto Era
Samurai swords produced around 1600 are considered shinto or new swords. During the New Sword era in Japan, the uchigatana evolved into a pair of blades worn at the waist. "