So: For Japan. In addition to the Type 79 Ko Gata (FT-17), we have:
The Type 87 Ko Gata. This is the Renault NC-1. Granted, If Japan is going to attack France, then just use a house rule to not use these tanks. Or just use them and forget about it. They enter service in 1927.
The Type 87 Chi-I. This is Japan's first home built tank. A multi-turret design of limited combat capability.
The Type 89 Ko Gata. This is the first version of the WW2 Type 89A Medium Tank.
Well known Austin-Putilov Armored Car. Built jointly by Britian and Russia, the Japanese were also a prime user of these cars.
Soviet T-18 Light Tanks. A Company of these were deployed to the Far East in 1929, when it was thought war would break out between the Soviets and Japan.
The Light Tank M1918, better known as the Ford 3 ton. With a 2 man crew and a .30 cal machine gun, this tank is all but useless except for guarding rear areas and light infantry support.
And the US Medium Tank Mod A M1921. An esperiment, only one historically produced. A very ambitious tank, it had many features found on later US tanks. However, it was a failure.
Also present in WPO are the Medium Tanks T1 (also known as M1921 Phase II) and T2. These three tanks and the Type 87 Chi-I were all experimental tanks that never saw active service. However, in WPO, they can see limited service. Japan receives the 4th Tank Chutai (Ex) equipped with the Chi-I, and the US the 15th US Tank Co (Ex), equipped with the M1921 and upgrading to the T1 and then the T2. Note however, this tanks build at a rate at once a month, and are not designed for active use.