Alt-RN building plan for the 1930s and 1940s

A few points:

Vanguard
Vanguards only make sense of any kind when compared to nothing at all or continued Rs. As a fully-armoured battlecruiser/fast battleship, it was a fine vessel, but the 15"/42 was at the end of its development life. When first contemplated, the battleship wasn't nearly as dead as some would think. It was in some ways a better deal than 2 supercruisers, but they did have the advantage of there being two of them. The optimal BB for the RN is the Lion.

KGV
The particular situation of the KGVs (12 x 14" then 10 x 14") came from rearming first and fastest. The decision to go for 14" over 16" was driven by finance to some degree, but the difference was not truly substantial - they never had to fight an enemy ship that couldn't be killed by 14" gunfire. However, given the opportunity to choose between the two, the RN would have gone for 16" for the advantages involved. It would not have any substantial bearing on their postwar service life.

Washington Naval Treaty
Washington was an issue, but not an existential one. The treaty that really came back to bite them in the backside was the 1930 LNT and the sheer mistake that was the 1936 LNT. The former constrained warship size artificially and had a negative impact on cruiser numbers, whilst the latter was doomed from before it began. The most striking impact of the WNT in some ways was the blow of the 10 year building holiday on British naval firms and capacity, but the circumstances of the 10 years leading up to 1914 were not in any way normal or repeatable. Washington arrested ship size growth to some extent and froze designs until the 1930s artificially - many will have seen the graph of BB sizes with the general rate pointing towards Yamato sized vessels by the mid 1930s.

British Naval Rearmament
British naval rearmament was governed by the limits of the economy but was the largest in the world and darn impressive in any terms...apart from comparison to the massive USN expansion of 1940 and WW2. 10 fast battleships ordered (only 6 completed) was well in advance of any of the rival states (Germany 2, Japan 2, Italy 4), but wasn't the limit of what was planned. The issue is that the war came earlier than planned and the Fall of France lead to the cancellation of quite a bit of construction plans, among other events; once conflict began, the decision was made to go with the fleet that was possible, rather than what could be built for several years down the line.
Bottlenecks existed in heavy guns/gun pits and armour production, as mentioned in the Crystal Eye thread. This came from a willful destruction of previous capacity, which was considered over-capacity in the circumstances of the 1920s/Great Depression/International Peace and Amity period, but at the end of the day only acted as a constraint on BB production rather than an absolute ironclad refutance.

A shedload of money was spent on the RN in the lead up to war, but much of it ended up not showing its true value due to timing and circumstance. There was no notion that the war would always begin in 1939 or even 1940, certainly not from the position of 1935/36 when rearmament began. If the process is kicked further back by 18-24 months, we'd see some different outcomes.

Conclusion: It isn't that there was no enough money, but that it was spent early and didn't end up showing true bang for buck. There were some decisions driven by finance within an overall prism of rearmament, but it wasn't a true sword of Damocles.

Steve,

Vanguard and any putative sisters worked because of the availability of slips and guns, but the armour bottleneck is the nasty part that crops up to prevent them being a completely ideal solution. The design of the ship herself with the exception of the main guns was very modern and right up there with late war/early postwar cutting edge battlewagon design.

The 15"/45 was worked on from 1935 onwards, but the 35,000t limit was artificial and extremely limiting on nations that followed the Treaties; on those that were more flexible or cheated outright, it was less of an issue.

Yes, the RN faced block obsolescence, but it only cropped up from the early-mid 1930s, long after the political memory/impact of the high-minded thinking of the Treaty supporters. At that point in the early 20s, the 13 x 15" ships were seen as pretty darn decent. If the Royal Sovereigns were repeat QEs, then the worst part of the block obsolescence of the remaining fleet is butterflied.

Bigger issue: If I might slip into my own terminology, at the WNT, there are 12" dreadnoughts, Gen 1 superdreadnoughts (13.5" and 14") and Gen 2 superdreadnoughts (15" and 16"). The first lot were always going to go and the RN was glad to see them go. In the second category, Britain had 14 (4 Orion, 3 KGV, 4 Iron Dukes; 2 Lions, 1 Tiger), the USA 9 (2 New York, 2 Nevada, 2 Pennsylvania, 3 New Mexico) and Japan 8 (4 Kongo, 2 Fuso, 2 Ise). In the third, Britain had 13 ships, the USA 5 (2 Tennessee, 3 Colorado) and Japan 2 (Nagato and Mutsu). I've taken the liberty of grouping the Big 5 together from the other USN Standards, but the 7 USN ships with all-or-nothing protection are certainly worthy of comparison to the QEs.

From this number, the IJN and the USN kept the lot for service in WW2. They got far better use out of their 14" ships than the RN got out of their 13.5" vessels. However, of that British number, the four Orions and 2 Lions were obsolete or flogged out by 1919 anyhow, which puts them back to effective parity in that category. Without the extention of the WNT, the 13.5" KGVs get replaced by new construction in the early 1930s and the Iron Dukes from the mid 1930s by something better. As you point out, it is the continuation of the building holiday that really hurt the RN more than other powers.

The other big hit on the RN was the Rs being inferior throwbacks that swiftly became second or third line capital ships. This would have been bad enough had the RN retained its 2nd generation ships, but the nature of the Treaty did write them into a corner.

Britain's construction programme wasn't too little, but by nature of the LNT, it was constrained and delayed (I'm looking at the KGV delays here). It ended up being too late, but this only became directly apparent well into the rearmament process. Kicking things off 24 months earlier would change a great deal of how we view the process.

Changing the policy of appeasement and having a go at Italy would dramatically change a great number of factors.