The Royal Navy at the end of WW1 had Numerous obsolete cruisers many still using coal and totally unsuited to what was understood as modern warfare . The Royal Navy Had recently begun construction of two modern cruiser designs . One was The Hawkins class and the other was the Emerald class .
The Hawkins class was of excellent range and speed compared to proceeding classes . The 7.5 inch gun was a good design but suffered from being hand loaded and trained single mounts . As speeds and ranges increased this became more and more unacceptable . It is worth noting that at the time of design in 1915 the 7.5 inch was chosen as an intermediate cruiser able to overpower German ships with 7 inch guns . The Treaty cruiser used the 8 inch calibre as a maximum and a 10,000 ton displacement . For the purposes of the Royal Navy the Hawkins was too much ship for not much gun . The Follow on Heavy cruiser design was the County class that was forced through hull design to be longer then for example the US Cruisers in order to have more fuel efficient engine to speed ratio's . (The Royal Navy was always able in this era to achieve better SHP to Speed for a given displacement .) .
The Emerald class was a brilliant scouting cruiser with very high speed and excellent range . Again the single 6 inch mounts are inadequate .
What I am proposing is that a universal cruiser design in introduced with the intention of maximizing the numbers of cruisers and the versatility of the design . If instead of the County class they instead go with a three twin 8 inch turret(one forward and two aft) design on 9,000 tons (York class plus armour ) . If designed for three single 4 inch AA guns per side and a pair of quad pom poms on centreline mounts (one in front of the bridge and the other in a super firing position forward of the two aft turrets. You could end up with a very good ship . I personally hate the amidships Royal Navy floatplane hangars and mount however for the time they are very good so I feel they should be retained . Allow for two Walrus size aircraft . Also the good old quad Vickers 50 cal could be mounted on top of these hangars .
Design the triple 6 inch to fit into the same barbette as the 8 inch .
With 450,000 tons the Royal Navy could conceivably build 50 cruisers . This would have required the Hawkins for example to be converted into a sub 10,000 ton carrier . Expect a 14 to 20 aircraft air group.
. By WW2 this would directly translate into 50 cruisers compared to 29 modern ships . With construction beginning in 1927 you would need to be building 4 per year . This would also improve strategic construction .