Yes, Japan is planned to get three versions. Himiko proves it. The name Meiji proves it.
Antiquity Age
Yamato or
Heian Japan should be the name, but both will need to be represented. Altough Jōmon was teased in the recent Dev Diary, I believe the team will have little to work with other than beautiful pottery. Yamato is the best choice because of the spectacular
Kofun tombs (Unique Improvement)
and the Heian period can provide the units. The Unique Military Unit is a bit of a problem indeed. The only early unit of note that I can suggest is the
Sōhei (warrior-monks with naginata and a head cowl). They came into existence from the
Heian era and onwards.
The Unique Civilian Unit should be a
Great Poet (Kajin). Each will produce one or more Great Works of writing. Combine this with an ability that gives more culture on Great Works of art and you are all set for a cultural game.
Associated World Wonder:
Hōryū-ji
or Tōdai-ji
or
Yakushi-ji
or
Byōdō-in
Exploration Age
Sengoku is too tumultuous, so either
Kamakura where the first Shogunate was established or
Edo where the unification of Japan was completed. The problem with Edo is that it touches the Early modern era, but it comes before the Meiji period anyway. The Unique Military Unit definitely needs to be the
Samurai with a katana (although the unit could use both katana and yari since it will replace the Men-at Arms) who will wear richly decorated kabuto with datemono as well as beautiful menpō and hanbō face masks. A combination of kosen dō (armour with scale) and tosei dō (armour with plates) would look varying enough with sashimono that have different mon on them attached to the back of the two armours.
Another option is the
Ashigaru, but I prefer the infamous elite Samurai over them. Feudal Japan without Samurai is like Rome without Legions.
Now for the Unique Civilian Unit. A mounted
Daimyo Commander wearing a moustached menpō and carrying a tessen or a gunbai war fan with two Ashigaru flag-bearers beside him is perfect.Since there will be three versions of Japan, the one in the Exploration Age will be Militaristic and Cultural, so the Daimyo is suitable.
The other option is the
Shinobi, ten famous Shinobi will be picked for this unit. They will be unseen to adjacent enemy units, with more visibility and the function of each will vary from destroying the fortication of a city to damaging all the districts and worked tiles around a city cencer of the target city to assassinating an adjacent enemy Commander to giving a combat penalty to an enemy Commander's force to making enemy units inside a city immobile for two turns to gaining +1 insight depending on the owner civilization of the city that is targeted.
Unique Quarter:
Jingū-ji (shrine-temple complex with a pagoda)
or
Tenshu (Unique Improvement similar to the Donjon that will be based on Osaka Castle)
Associated World Wonder:
Kōtoku-in
or
Himeji Castle