Pistols
Tier 1 (E): Type 26 Revolver
Tier 1 (L): Papa Nambu
Tier 2: Type 14 Nambu
Tier 3: Type 94 Nambu
Tier 4 (E): Type 1 Pistol
Tier 4 (L): Type 2 Pistol
Tier 5: Type 5 Pistol
[Type 5 Pistol ‘Suigura’]
Submachine guns
Tier 1 (E): MP18
Tier 1 (L): MP28
Tier 2 (E): S1-100
Tier 2 (L): Type 100/40
Tier 3 (E): SIG 1920 (50 Mag)
Tier 3 (L): Type 1 SMG (50 Mag)
Tier 4 (E): Type 100/44
Tier 4 (L): Tokyo Arsenal Model 1927 [PREMIUM]
Tier 5: Type 2 SMG (50 Mag)
[Tokyo Arsenal SMG Model 1927, 50 round drum, 1200RPM]
Rifles
Tier 1 (E): Type 30 Rifle
Tier 1 (M): Type 44 Carbine [PREMIUM]
Tier 1 (L): Type 38 Rifle
Tier 2 (E): Type 1 Rifle
Tier 2 (L): Type 99 Rifle
Tier 3 (E): Type 38 Rifle w/grenade
Tier 3 (L): Type Ko Rifle (10 mag)
Tier 4 (E): Type Otsu Rifle (10 mag) [PREMIUM]
Tier 4 (L): Type Hei Rifle (10 mag)
Tier 5: Type 4 Rifle
[Type Hei Rifle with 10 round Mag]
Light Machine Guns
Tier 1: Type 11 LMG
Tier 2 (E): Type 91 LMG [PREMIUM]
Tier 2 (L): Type 96 LMG
Tier 3: Type 97 LMG
Tier 4: Type 99 LMG
Tier 5: Shisei LMG
Shisei LMG, also has an option of mounting a frontal shield
Tanks
Tier 1 (E): Ha-Go Mod. 1938
Tier 1 (L): Ke-Ni [PREMIUM]
Tier 2 (E): Chi-Ha
Tier 2 (M): Chi-Ha Kai
Tier 2 (L): Chi-He
Tier 3 (E): Ho-I
Tier 3 (M): Chi-Nu
Tier 3 (L): Chi-Nu II [PREMIUM]
Tier 4 (E): Chi-To
Tier 4 (L): Chi-Ri
Tier 5: O-I Heavy
Fighters
Tier 1 (E): A4N1
Tier 1 (L): A5M4
Tier 2 (E): A6M2
Tier 2 (L): A6M3
Tier 3 (E): A6M5
Tier 3 (L): J2M2
Tier 4 (E): J2M3
Tier 4 (L): N1K1-Ja
Tier 5 (E): N1K2-Ja
Tier 5 (L): A7M2 (4x 20mm)
Close Air Support
Tier 1: E13A1
Tier 2 (E): D3A1
Tier 2 (L): B6N2
Tier 3 (E): D4Y3
Tier 3 (L): B7A2
Tier 4 (E): Ki-102
Tier 4 (L): P1Y2
Tier 5: Ki-93
I would like to add a disclaimer regards to the O-I Heavy Tank. Whilst there are no pictures of it in real life, there is actual documentation about it being tested. The tank was fully built apart from the roof armour but was scrapped later for metal which japan was short on. The O-I was origianlly suppose to operate as a moving pillbox on the plains of Manchuria vs USSR but since the war shifted to the Pacific, there was no need for such a vehicle and the metal was more important. Its a viable Japanese tank alternative that would allow japan to face IS-2, M26 during late stages of the war without giving them post war vehicles.
The O-I is a very slow big tank with 150mm frontal armour and 75mm side armour. Its main gun is the not so uncommon 150mm Type 96 Howitzer with a very long reload.
All things considered, overall the O-I will still be overall weaker against IS-2 Mod 1944 or M26 Pershing. O-I advantage will be its greater anti infantry potential.