I'm unsure why some people seem to think that IRL that none of these countries stockpiled strategic resources. All countries stockpiled strategic resources to greater or lesser degrees. Germany wanted to stockpile 10 times as much as they did, they simply lacked the foreign exchange to purchase it, but they would have if they could have. Even the United States passed a Strategic Resources law in early 1941 to stockpile 15 strategic resources, 12 of which the US did not produce itself in any quantity. Great Britain had vast fuel stocks all over the world to fuel the British fleet.
I think this would have been a great area for the devs to align stockpiles with National Decisions, to require industrial capacity to build storage and transportation systems, and to balance what was, admittedly, a less than ideal system in HOI3. But rather than design a better system they simply threw stockpiles out.
Similarly there were a lot of good ideas in the HOI3 supply system, but also a lot of flaws. Rather than try to fix the flaws and produce a robust system that offers great strategic depth, models the real life decisions that needed to be made at the highest levels (Do we give the fuel to Patton or Montgomery?), and would also add depth to the strategic bombing campaign, they, again, just threw out the whole system.
I won't talk about the whole fuel debate, I have posted enough on that already. But lets look at the supply system as it is going to be. I think there is some merit in the idea of supply regions, and that large cities increase the ability of defenders to hold out. But lets look more closely at the actual supply itself. Where does it come from? As far as I can tell it grows on the ground like mana. If it represented only food and perhaps clothing, items that the civilian population produces, that might have some reasonableness to it, but supply surely also has to include military stocks like ammunition doesn't it? And regardless of what it represents, how do I make more of it? Is the mana-like supply that appears from the ground now a more-or-less hardcoded restriction on how many divisions I can have? Shouldn't the player have a lever to make more or less supply at their command? (Not without cost of course, please don't assume I mean it would be "free".) The player can make more or less divisions, air force and fleet, but not more or less supply? Do people really think this is a good thing, not just to agree with what has been offered, but to actually agree that such is good game design?
Those of us that feel as I do don't want Total War: World War Two. I want something deeper, more detailed, with more options and ways to interact. HOI4 is becoming so automated, that between making a Battle Plan, assigning one of your handful of leaders to it, assigning some divisions, and letting it go (and yes I know you can micro more than that, but the Battle Plan system rewards those that use it over those that micro). not having to worry about supply, etc., I'm not sure what Paradox thinks the player will be doing.
At this point I'm hoping for good mods.