I'm going list a couple of specific things I think should be in the game
- Every country should be able to achieve a basic universal tech slot count based purely of factory count to represent the access to technical resources that would occur when you have acquired control of a large number of factories. This should be based on an effective factory count taking into account occupation and compliancy. I don't really care about the exact rules, just that small countries conquering a lot can get tech slots. This should perhaps be balanced by small countries current tech slot count being more restricted.
- When a country is conquered the conquering country should be able to acquire a free build licence for anything being built in that country to represent the practical consequences of gaining control of the factories actually doing it. Potentially even acquire existing production runs. Free licences is probably a reasonable way of simulating the research benefit of gaining control of factories that were already making stuff. It would do a good job of simulating that you now know how to build a specific aero-engine but that isn't the same as your engine makers necessarily understanding how to design one.
As to the former point, I'd argue that there wasn't a direct connection between the military industry and technological development during the war itself or even necessarily the prelude. France notably had a much larger military industry than Italy, though the Italian military, in HoI4 terms, "researched" a heck of a lot more techs, even before the fall of France. China's military industry was far larger and more sophisticated than most would give credit for before and during the Sino-Japanese war (though it's hard to get exact numbers, it's quite likely China produced more rifles between 1936-1941 than the US did) but you could make a strong argument that in HoI4 terms, they'd have
no techs at all, since techs imply domestically developed production and China never really had any of that, just production of either licensed or cloned weapons in addition to those purchased from other nations.
Simply having facilities doesn't really make "techs" here, after all. The "techs" are domestic ability to produce something anywhere within your nation feasibly if the requirements are there- if Lithuania ate the Soviet Union by some miracle, you could argue (so long as the people with the knowledge stay and are loyal) that they could continue to produce Soviet tanks at
their facilities and probably obtain a lot of documentation for
maintaining them, but it's not like Lithuanian engineers and industry leaders would suddenly be bestowed with the knowledge. I think that'd be abstracted through... well, through politically cultivating local experts (i.e. research slots) and actually researching techs.
Though, that said, industry is certainly a prelude to what would be research in HoI4 even if not necessarily directly granting it (though I'd argue that this is typically already the case in-game given most research focuses have a factory requirement), and having some sort of research bonus based on captured equipment at the very least would make quite a lot of sense.
I'd agree to some extent with the latter point, but examples of this actually happening during the war are pretty rare and also pretty entirely Germany-centric, even if it does make some logical sense (it also makes logical sense why this wasn't often the case, because oftentimes it wouldn't make logistical sense to do so).
On
@Anony1200's point about new stuff not being designed I think he is missing the point somewhat. In tanks, ships and aircraft a whole assortment of new models were designed backed up by a whole pile of technology improvements in the underlying components - ie steadily improving aero-engines, tank engines etc. On other equipment we generally see a single new model of most things in the time period specified. This one generation forward tended to be for those countries that were still largely operating WW1 equipment. The only area of infantry equipment with significant innovation was anti-tank weaponry driven entirely by progress in tank technology. Progress wasn't in providing better tools for the same job, it was about continuing to provide effective tools for the same job. However, there was a steady stream of research and development of stuff often behind the scenes that nobody takes much notice of.
One point that hasn't been mentioned is that most actual technology progress is not about the design of the equipment but progress in how to make stuff. If you took a modern jet engine and showed it to WW2 jet engine researchers they would find the whole thing perfectly understandable but they would be at a total loss about how to make it. If you gave them a modern turbine blade they wouldn't be able to even work out exactly what it was they were looking at in terms of the metallurgy - they would know it was a turbine blade. A lot of the research in the game is not invention of a new engine design or anything like that, it is research into how to make such a thing.
No, I think you're missing the point I was trying to make- what I'm saying isn't that this process didn't happen or anything similar, but that the actual part of the world that these advances were being made was incredibly concentrated, that this was only really happening in a few countries, yet the game is set up (by design) for this to not be the case.
I mean, that jet engine example you mentioned in the post- if you use 1948 as the cutoff point,
4 countries on the entire world map ended WW2 with any kind of domestic production or even the expertise needed to produce jet engines, and one of those (Japan) never even did so en masse until much later. Even the Soviet Union was dependent entirely on, at the very least foreign-made engines, but mostly on foreign-made aircraft in the immediate post-war period for their jets. If you want to talk about a domestic military aviation industry that actually made any sort of new designs rather than just building foreign models off licenses in general, not just jets, that's really only 12 countries, which shrinks to 7 if you eliminate countries that only put out one or two domestic models, or strange edge cases like Heinkel making designs for Spain and Hungary based off designs the Germans declined to use.
You could find very similar situations elsewhere- arguably only 5 countries had any Mechanized "techs" by the end of the war, and one (Japan again) only did pretty small scale production. Even most countries that had armor never reached the 1944 model until post-war, or, in some cases, even the 1940 model. Of course, far more countries used these things, just not with the domestic research and production that HoI4 implies, but through licensed production or simply lend leasing, which, as stated earlier, were very major cornerstones of both Allied and Axis war efforts that are not very well represented in game- I mean, the US lend-leased so many halftracks that despite very few Allied countries having any sort of domestic production of those vehicles (or, for that matter, unoccupied production of any kind), the foot soldier essentially disappeared from western militaries immediately post-war.
And that's the real issue, I think- that this is something that kinda needs to be, to some degree, "gamified" and divorced from realism, but there definitely needs to be more of a balance than there is right now. Bulgaria shouldn't be forced to exclusively just use German, Italian, and Czech equipment without any sort of local production or ability to do so, even though you could suggest probably rightfully that's the realistic situation (trust me, if they could've, they would've), but Bulgaria should definitely be able to play that way, which they aren't currently- and if they were, the Norways, Bulgarias, or Generic Focus Trees of the world would certainly have less to complain about.