The Nagara class were an extension of the previous Kuma class with several upgrades that had been deemed necessary. The main difference between the classes was the fitting of the new 24" long lance torpedo tubes from new where the Kuma class received theirs as upgrades over the years.
The Nagara class as completed above closely resembled the previous Kuma class. Below shows the Nagara with refits through to 1934. Aircraft handling facilities, glassed in bridge, gun directors, and the first minor AA weaponry being fitted. Beside the fore funnel are two 80mm AA guns while in the 1934 drawing these have been replaced with 25mm weapons.
By 1943 the changes to the near obsolete ships (they were 20 years old) had little further value in them. Some were used as destroyer and submarine depot ships, a static role in harbour, while others were still used as destroyer leaders to the older destroyers still in service. Those ships still used at sea were fitted with some forms of radar, had guns removed to allow extra 25mm AA guns to be fitted. Some had the two twin 24" mountings forward removed and plated in, the aft twins being replaced with two quadruple mountings.
The only one of the real life class to receive a full AA modification was the Isuzu as shown below.
To my way of mind these would have been taken in hand after the Kuma class have had their rebuilds in 1939-40, and then the Nagara's could have had their rebuilds in 1940-41.
.png)
The rebuilds for this class could be much fuller than the previous Kuma class. A full suite of Dual Purpose weaponry, radar, new bridge structures, new quad torpedo tubes,. Remove the antiquated mast structures and aircraft and handling equipment. Trunk the funnels together to give a better draft.
