Sorry if any of these duplicate other people's suggestions or design changes since TFH.
Production- Factories might produce specific equipment types which pool for units to draw from. Factories cannot retool without a time penalty. Tech develops new weapon types. Current relation of theory and practical is nice touch.
Production bonus from specific provinces is nice, nicer if implemented in an historical way eg Sweden resource I believe should be iron ore, not tungsten. Automotive bonus surely shouldn't be gained where no factories are in the province. etc etc.
Blockaded Nazi Europe
Critical Axis resources are manganese, food and oil. Blockaded Europe should not be sustainable indefinitely without conquest of Ukraine. Not sure how you'd implement a rule for this, maybe make supplies less abundant and increase discontent/revolt risk in occupied territories dependant on annual harvests.
Manganese I think warrants inclusion as a distinct resource on account of vulnerability of supply for the Axis. Once blockaded by British Navy, Axis sources manganese only from Russia. If at war with Russia and not in control of Nikopol, Axis industry was on a timer with a risk that all steel dependent industries would close down. Over, kaput! Loads of opportunities to game this if not implemented carefully.
Tech
Tech is a really nice idea but I for one would certainly like to see it implemented with more historical accuracy/plausibility. I get the idea historical reality is distorted to make a neat number of tech advances in each type. Sorry, this aspect doesn't work for me. I've, as yet, only played Axis, hence the fixation on examples of theirs.
If I got this right, Germany cannot create paratroops without researching the PaK 40 ATG. If that's true, you know that ain't right!
Unfortunately there are shedloads of strange designations and misleading pics.
Einstossflammenwerfer (1940 Assault Weapon tech) was a late war militia device of last resort, not an early war tech advance.
The Type IX uboat replaces the Type VII when they were produced concurrently as long and medium range varients respectively.
Model 1940 uboat hull is the Type XXI uboat? This appeared so late it never fired a torpedo in anger. Late war production difficulties resulted in very few finished units but if ironed out this was a very advanced design.
Type II uboat crews cannot upgrad. Please!
As above, if industry can produce and pool equipment, with a bit of crew numbers adjustments equipment swap outs would be really nice.
Zaunkonig is an accoustic torpedo. It comes with, I think, 1940 torpedo tech. Under Secret Weapons tech you find acoustic torpedo which is a 1945 tech and gives advances well beyond that of the Zaunkonig which was really a bit of a flop as a merchant sinker.
Again, torpedo types didn't really replace, so much as augment each other.
Likewise, aircraft development is strange. German interceptors are 109E as of 1941, with dual purpose planes 109Fs and Gs. The Fs and Gs are slower, I think, than the Es. Hmmm. Really, by 1941, there were a few 109Es of various types used as FBs as well as Bf110s which don't even seem to be in the game. Fs and later Gs primary purpose was as interceptors, I think.
Night fighters were a variety of twin engines planes for the most part, many converted bombers initially. haven't seen them yet as of 1941.
Allied Cooperation
Clearly, losing all restrictions on allied control would make for a very unrealistic scenario. However, operational control of units was often given to allies. To complement Expeditionary Force, which I've yet to see the AI offer, what about making the Operational Control of units purchasable with diplomatic points? Casualties suffered while under allied control might generate inter-allied tensions risking withdrawal of troops and perhaps in some cases, alliance rupture. That way, you get control of units but you'd better be careful with them if you want to stay friends
Units
I'm sure I'm not the only one to mention this, I'd love to see the game name units historically, not just division and regiment names but also designate regiments, battalions etc by their name, not brigades.
From this, I'm afraid the combined arms bonus is very gamey. All divisions were by definition combined arms but the brigade structure does not allow all the components of a division to be represented. Neither are there sufficient divisional slots to add all the historically organic support units. For the sake of simplicity, these might perhaps be understood as within the division's regiments/brigades. Local pools, perhaps by Theatre, of attachable/detachable support units would be very nice indeed.
Why are Trotskyite and Bukharinite tendencies in Russia listed as "counter revolutionaries"? History has definitively shown the Stalin faction to be just that. Have I lost my sense of humour?
Pop ups
This is a major butt pain. Pop ups are very necessary but they arrive in the middle of the screen where I tend to focus, very conventional, I know, sorry. This interrupts concentration and when accidentally clicked on as they, err, pop up, opening up another pop up box. Could we have an option to have them at the side or in a corner?
FOW
Un-fogging of war lasts too short. Last recce/intel should stand, maybe with age info in a tooltip.