Bullethead
Storm Eagle Studios
But construction strategies were very largely a factor of available technology, and the development especially of machinery technology had a huge impact on the history of cruisers.The problem with determining what was and was not considered for design and what was adopted for construction was the lack of actual combat experience which contemporary navies were able to draw....Thus the construction strategies were constantly changing.
In the latter 1880s when the predreadnought era really began to stabilize (as in the general outline was in place, although there was still a continuous string of detail improvements), machinery was big, heavy, and hungry for the power it produced. As such, in those days, the only viable design for a fleet scout or commerce raider/defender able to go several knots faster than the battleline for hours, perhaps days, on end was the AC. These displaced nearly as much as BBs but were longer due to finer lines. Only such ships big ships could carry the necessary power and the fuel it needed, and even then had to have lighter guns and armor. They did build small cruisers back then, but most of them weren't any faster than BBs due to the inability to carry sufficient power and fuel. Besides, the fleet CL role hadn't yet been invented because DDs/TBs weren't yet capable of working with a fleet. Thus, such small cruisers were mostly for patrol work. In fact, for a couple decades to come, navies would still be bulding masted small cruisers for such work.
Time passed, machinery improved, and that changed the picture. By around 1900, it had become possible to build small cruisers with the speed and nearly the range of ACs. DDs had also grown enough to work with the fleet, but needed fast flotilla flagships to control them, due to their nonexistent bridge space. IOW, machinery development created the niche for what would become the CL.
CLs were much cheaper and thus soon more numerous than ACs, and able to perform almost all AC roles, plus could do the new job of flotilla leader. As a result, navies decreased the number of ACs they built in favor of CLs. After all, an AC was not only about as expensive as a battleship, but was serious overkill in most of its jobs. How big a gun do you really need to capture a merchant or sink a pirate dhou, for example? Thus, for example, whereas before the RN was building about 1 AC per BB up to about 1902, afterwards their new AC:BB ratio declined to about 1:3. The difference was being made up in CLs.
I see the growth of CLs as just part of the general trend of all types of ship to get bigger over time. The combat (as opposed to recon) role of CLs was killing DDs; as DDs got bigger, CLs had to grow, too. And because so many were needed, they only grew just enough to keep pace, to keep costs down. As such, they didn't grow very much during the war. Note that from the Arethusas all through the dozens of C and D classes, CL size had remained between 4000-5000 tons, the only real change being going to all 6" guns.With respect to light cruisers, they were becoming larger and progressively armed with bigger guns over time. In addition to the Cavendish class mentioned, there is also the Courageous class which went the whole hog and mounted heavy guns in a light cruiser. Thus the trend in cruisers may have eventually led to intermediate guns being adopted.
In this context, the Cavendishes, Emeralds, and the never-built designs of 1918 were statistical outliers, not trend-setters, as their sudden doubling in size over previous CLs should indicate. As mentioned earlier, the Cavendishes were not at all intended for fleet work, but were specialized hunters of commerce raiders in the far seas, precisely to avoid having to deplete the fleet's stock of normal CLs for this job. The Emeralds and 1918 designs were even more aberrant. The Emeralds were designed solely to catch Brummer and Bremse, while the 1918 designs were merely ideas to match a rumored new German cruiser with medium guns, should such a thing ever be built.
Note that all the while, however, the RN was still building C and D cruisers as fast as they could, laying many down after starting the bigger ships. They even completed a fair number after the war and had more still on the stocks when the war ended that were canceled, although they certainly would have been built had the war continued, and no doubt more would have been laid down. Thus, IMHO you can't use Cavendish et al as guides to the future in a treatyless world. The RN apparently thought it's existing ~4500-ton CL formula was perfectly adequate for CL duties, but that Their Lordships hadn't quite lost all of Fisher's wild hairs. The Cavendishes weren't especially liked in service (one was even completed as a carrier) and the others were just examples of the common naval folly of building a ship to fight 1 specific adversary instead of being useful in general.
This seems to have been what most navies did. The US, Germany, Japan, and Russia, besides the UK, all had large late-war CL programs in hand. Most of the German and Russian CLs were never finished, but the available German CLs were gobbled up after the war by France and Italy, which hadn't yet built any (or many) of their own. And of course BBs were getting bigger guns the whole time, so were also getting more armor.If I personally was procuring warships in this period, I would be emphasising an increase in the construction of light cruisers and protection/armour in my Battleships. I am not entirely convinced that contemporary navies and politicians would have gone down this route though; if for no other reason that they did not have a copy of Jutland to play!!!!