Meant to chime in on these earlier, but better late than never!
So what you're saying is the fast wing role was put on the QEs and the battlecruisers relegated to cruiser leaders. So the new battlecruiser roles are raider hunting and leading cruisers squadrons. Fast forward that 10 years. G3s are the fast van, what's going to be the cruiser killers and cruiser leaders. Hood, R&R?
The QEs were originally intended to follow what was the RN's normal shipbuilding programme during the 1906-1914 years, which was typically 3-4 battleships and 1 battlecruiser per year. FWIW, the very first battlecruiser, HMS
Invincible, was a 25kn ship. The QEs were originally supposed to be configured like the preceding
Iron Duke, class, but it was found that 8× 15" guns throw a heavier broadside than the 10 13.5" guns mounted by the
Iron Dukes. By using all oil firing boilers instead of mixed firing, the QEs could get up to a theoretical 25kn. It was thus decided they could form a fast battleship wing, and the battlecruiser was dropped from the 1913 programme and a 4th battleahip was ordered in lieu, and a 5th when the Federated Malay States offered to fund it.
In practice, the QEs did not succeed in their lofty goals. They were overweight and had blocky battleship hull forms, and could only make 23.5-24 of the 25 intended knots. Battlecruisers also got faster, going from 25 kn to 28, 30 and 32 kn ships, so they could not keep up and were thus tied to the slow battle line. After WWI, it was affirmed that an intermediate speed between battlecruisers and slow battleships was of little to no additional usefulness, as if they were to give chase, they would leave the battle line behind, but were not fast enough to operate with true battlecruisers.
However, they proved that all-oil firing and fewer but bigger guns are very useful, and although it wasn't possible in 1913, that a true battleship with battlecruiser speed could eventually be possible- the QEs, after all, were mightier than
Dreadnought or any Dreadnought built before her, and nearly as fast as
Invincible.
The Alaskas are a bad example of super cruisers for a few reasons. Call up CalBear and he'll find several more..
But at the end of the day the ships they were designed to go kill just didn't do what was expected. The Japanese didn't go for commerce raiding in the sense Germany did in ww2. They also lacked flagship abilities. They were the size of the Scharnhorsts.
To me at least, the
Alaskas were not awful ships. They were very good super cruisers. They were faster than almost anything afloat bigger than a destroyer. Their 12" guns were far superior to the USN 14"/L45 and delivered comparable belt penetration and superior deck penetration vis the USN 14"/L50 in a lighter package with a faster rate of fire. Their topside protection was excellent, as was their radar and AA suites. There are, however, two huge flaws to me.
The first is that they only had cruiser style underwater protection with compartmentization; no liquid-void system or torpedo belt. That would leave them one fish wonders, especially if hit with a Long Lance. At 808' long, they were longer than any USN battleship bar the
Iowas, and 80' longer than the next longest, the
North Carolinas. That leaves a battleship sized target with cruiser protection.
The second was the cost. Their gun system, made from scratch, was the most expensive in the USN, more expensive than the 16" L/50 Mk. 7 on the
Iowas. In fact, an
Alaska cost 2/3 - 3/4 as much as an
Iowa but were not 3/4 as capable. It would have been a much better investment to complete
Illinois and
Kentucky rather than
Alaska and
Guam
The Lexingtons were the definition of a glass jaw. The Americans took exactly from jutland, said hey look none of the 9" armour belts got penetrated so clearly we should put a 9" belt on our battlecruisers. Nobody seemed to notice initially that hey all the german battlecruisers had 11 inch guns and every battlecruiser since has had 15" guns or higher surely we should armour against that instead? Which seemed to dawn on them later in construction.
In almost any fight with an enemy battlecruiser apart from the G3s it would be a case of who hits first.
The problem the Americans face in 1920 is that Britain and Japan have lots of big and fast ships and the USN has none. The Standards, while very well armed and armoured, were 21 kn ships with stubby hull forms, so no more speed could be coaxed out of them without huge reconstructions. The USN has nothing capable of counter-scouting, and a CA stands no chance against a
Kongo or
Renown, let alone
Hood, Amagi or G3, nor do they have anything that could chase off a fast squadron attempting to harass the battle line and run. In these early days, something is better than nothing, before a "Sims Doctrine" (Compromise on nothing but displacement) fast BB is built.
Again, same problem the Brits run into: the Japanese only have six battlecruisers (the last two Amagis are unlikely to be completed as battlecruisers) and the Americans were seriously considering thirty 8" cruisers. And while the Japanese don't have the trade protection issues the Brits have, they were very interested in counter-scouting and breaking through American cruiser screens. The former is what led to the Furutakas to outfight the Omahas, and the Japanese aren't simply going to stand pat on that front with 8" cruisers being cranked out; the latter is what their CAs were actually supposed to do in their Kantai Kessen plan.
Compounding the issue is that the Japanese were very fond of using battlecruisers as a fast wing of the battle fleet. While the Kongos would probably be used in distant action, the Amagis are going to be tied to the battle fleet and thus held back.
The problem here is that Japan can't afford to have a large buildout of heavy cruisers and battlecruisers; there isn't enough Yen for both. Money makes it pretty much an either-or choice. I could see a few heavy cruisers, but in an unrestricted environment, the battlecruisers will ultimately be more useful in overpowering enemy scouts and breaking through screens. The IJN is worse off building CAs in a less restricted environment, let alone an unrestricted one, as their 4-8 bigger heavy cruisers still can't beat 30 USN ships, or even 20 if the USN keeps some in the Atlantic.