Both countries, and British with them, will make every improvement to their tanks that is feasible to do during the Summer and Autumn of 1940 (plus during the Winter etc). Germans will try to up-gun and up-armor their stuff, while French will try to do the same, as well as to introduce the better turrets if possible.
I'd guess that two H35s will cost at least as much as one S35, while needing double the number of trained crew
440 of S35 produced before mid 1940 is still very good. Too bad that French didn't doubled-up on the S35, foregoing the H35 all together, for yet another 600+- of the S35s instead of 1200+- of H35s.
French tank production, in numbers and let alone in tonnage was better than what Germans were doing, pointing out that they in fact that
they have had the plants/factories to make stuff. Unfortunately, best of the production capacity was used up for making the under 12 ton tanks crewed by two men each.
France didn't have had the time because they were defeated by Germany. As it can be seen, production of the serious tanks in Germany was also not roses and unicorns.
If the S35 can have a 2-men turret in the operative tanks in summer of 1940, that is a major boon for them. Having that in, say, October is indeed too late for 1940.
The 75mm gun on the Char B was a good start. An excellent start when compared to what the other people were installing in their tanks in the second half of the 1930s.
Pretty much on point for the price calculation (it's approx 2 H39s for one S35), with the required number of personnel being 33% (but only radio operators), if you look at number of trained crew it is indeed double.
Some of the documents I'm seeing in January discuss orders of automobile vehicles in 1939/40 and the industrial situation in late 1938 and late 1939, so they might clarify things a little bit (and experimental APX "materiel" for tanks in wartime which might clarify stuff about ongoing work re gun integration).
The case of the Somua remains a mistery because even as of 1940, the mobilization orders only go for 36/month while required monthly production ballooned for other types (even B1's mobilization orders increased to 100/month just after the declaration of war when it was realized that the originally envisionned 50/month would not suffice). I know one document I intend to see will at least clarify the prewar situation (it was suggested to procure more numerous times). The fact that it was only required for armored divisions isn't a sufficient reason since part of the Infantry requirement for Hotchkisses was as a stopgap in the DCRs pending the arrival of enough B1s, not just as a light infantry tank for the independent infantry support tank battalions.
The 500/month figure for H39 was never seriously considered. What happened at declaration of war was that the mobilization capacity for Renaults was unchanged (120/month) while that of the Hotchkiss was sharply increased upon realization of the sheer needs for tanks and the fact it was the simplest tank to build. In fact Hotchkiss was even told not to acquire the tooling for 600/month since it would be useless (they would face bottlenecks elsewhere and the Army didn't want that level of priority).
Turrets were the one thing meant to change significantly in the Summer 40-Spring 41 period, while everything else was for 1941 instead*.
The trend was towards almost no castings or only for small pieces, and instead welded, bent and pressed assemblies (ARL 2, 37 FCM, ARL 5).
For the Somuas, we know that industrialization of the ARL 2 C (Cavalry) turrets was ongoing in May and their deployment pretty much imminent (July/October). The matter was under investigation before the battle for the remaining B1 Bis, but it's not known if industrialization of the ARL 2 and modified roof plates was ongoing for this type.
The elusive ARL 5 was already envisionned for production as early as April 1940, but unfortunately, no documents can say where the industry was in May. A prototype was running.
All of these 2nd generation turrets share a simpler construction (reduced use of castings) as the most defining characteristic. Vision is improved insofar as the 2 PPL 160 episcopes (1 per side) and the rotating cupola with 3 vision slits and one binocular sight from the APX-4 are replaced with 3 PPL 160 (one in the rear door now) and a fixed integral cupola with a panoramic Gundlach periscope and 3 PPL on the ARL 2. Vision is always a particular subject for 1-man turrets however as the cupola is de facto the main observation post. ARL 5 is unknown other than the fac it has a fixed cupola.
ARL 2 at least is also tied to a new safer turret ring, and an improved electric traverse system (no clue yet if it faster or better for the actual traversing part, however it no longer uses the batteries so it was more convenient for battery management). It also included a ready supply of ammo for initial engagements unlike the APX-4.
In all cases, increased protection was solely the result of switching to rolled plate and potential improvements in shape. In the case of the ARL 2, you can somewhat cheat because it was a modular type prepared for 40 to 70/75mm thickness, so you could slap the thicker types on a B1 Bis and Somua even if you didn't change the hull armor (weight penalty: 700 kg tops on the B1 Bis, 1200 on the Somua but you go from 40 to 70mm).
APX-R (light tank turret) with 60mm of armor was once a proposal for an armored car, but you would need a new casting and it is apparent that it was to be replaced anyway.
The lessons' learned report after the battle exactly adresses Short's points (2 crew members at least, albeit still not mandatory on the light tanks, hybrid cupolas with features from the Germans AND 2nd gen French designs, gun mounts modified in favor of setups for shorter turrets like the Germans).
*the more appropriate summary for Summer 1940 and Spring 41 is
- generalization of long 37 on the light tanks
- continued increase in monthly production
- turret swaps
- S35-->S40 (mobility/quality of life upgrade)
- reliability/durability mods on B1 Bis plus increased fuel capacity
- industrialization and generalization of light tank radios and intercoms for the battle tanks at least
- major/minor suspension changes on the lights and potentiallybelly upgrade against AT mines (R35-->R40, new track for Hotchkiss)
Ironically, the French were spending 1940 precisely working on the areas we criticize them the most on, while ignoring those we praise them the most for. And it is also the exact opposite of the areas the Germans worked on.
Indeed, the book is overdue.