Amagi, Akagi, Takao and Atago.....
The Washington Naval Treaty, signed in February 1922, greatly reduced the tonnage allowed for capital ships in the signatory nations. The treaty also instituted a moratorium on new warship construction, but allowed both Japan and Koko to complete one warship over 35.000tons each that was currently under construction. Having no warships under construction to fullfill the allowances, Koko was ultimately allowed the transfer of one of the Capital ships under construction in Japan. With the IJN immediately choosing to complete Tosa as a battleship, Koko would have been granted one out of Kaga, Akagi or Amagi, as Takao and Atago were deemed not enough advanced to justify their completion..
Just days after the WNT ratification, a meeting between IJN and KnK Naval Staffs was called in Tokyo to dcide the fate of the three ships. As the IJN, unlike Koko no Kaigun, was also allowed to complete two capital ships under construction as Aircraft Carriers it was at least certain that all three would have been eventually built. At first members of the various Staffs were prone to complete Amagi and Akagi as carriers and to transfer Kaga to Koko no Kaigun upon completion, but the consideration of having the USN and the RN completing three and two 30+knot battlecruisers each ultimately led to the decision of granting Amagi to Koko. In August 1922 the deal was officially made, with construction on the Battlecruiser immediately restarted at Yokosuka.

I like but would you not have to name the ships in the WNT (and weights) or you run the risk of the IJN finishing Kii-class instead, I sure that the USN/RN will insist on specifics on what each side can build.

Sorry if you feel I'm nitpicking on a thread filled with such nice ships