Since HoI2 was developed i dreamed about something, that would be something between Vicky and HoI3, in the production part of HoI. I hoped for HoI3, but even there this never happened.
My idea was: Give the Player factories, that can produce War material. Lets say there are 3 kinds of Factories a Player can build. 1 each for Land, Air or Sea Units. The sea factories, would be nothing else as shipyards. Naval nations like USA/Jap/UK would start with many....Germany would only have a couple. A player could also build new shippyard, but it would need much time, maybe 2-5 years. So a Land Nation couldnt switch easily to be one of the Naval nations. Other Factories would be maybe easier to build...but still would need many ressources and Time (at least 1-2 years). Such Factories would then produce units...like in Vicky. Aircraft works would have a steady output of planes, per day or week. You would need all those planes as filling material for your Air Units. In fact you would still "produce" Air- or Landunits in the known build queue, but that would reperesent more the Administrative shell/hull of the later Unit. Like now, when the Unit gets into the build Pool, manpower gets removed from the MP pool, additional 100 Fighters /50 Bombers / 25 Naval Aircraft would be removed from the Aircraft Pools. Isnt the production time something else, as the time Soldiers need to get trained with their War material on Hand?
Over the time, and after you haver better tech, your factories can produce newer Planes. Maybe you would start with heinkel 51, then later BF-109B /D /E /F /K would come later, also Focke Wulfs, Me 262 and so on....
But how would this work with the pool? Maybe every of the Pools would have sub-pools, one for Fighter, one for Tac-Bomber, another for Strategic-Bombers....
So the Fighter Plane-Pool would show you something like this, when you plan to build a new Squadron:
Planes availiable for use in Air-Squadrons:
47: BF 109 D
267: BF 109 E
479: Focke Wulf 190D
12: ME 262
You can decide then what you want into the Unit. Until 100 units are possible. Chosing maybe over klicking the Aircraftnames...or over typing the numbers you want in your unit....or even better over define some rules, like:
"most modern first", or
"oldest first", or
"use only same type"
....
Then you would have to define also, what happens when the unit loses planes. What replacements you want for them. Maybe same rules as above.
So you would have Airsquadrons on the Map, like a Fighter-Unit with 62 Bf109E + 25 Focke Wulf 190D = 87 Planes together. The range and speed would be calculated like with Naval fleets, where the shortest range and slowest unit defines the speed/range for all, as they need to fly together. You could make "same type"-units and would then benefit from better speed and range.
In combat, the Game would calculate the Fight-Power with something like:
(62 x 1,4) + (25 x 2,1) = 139,3 total. You get the Picture.....they planes would still use the stats they have now in HoI3 (one for attack on ground...on naval..against air, but it would be calculated in sight of the the buildup of the unit. And the losses would hit also every kind of Plane. So maybe you lose then 34 Be109 and 12 Focke.
This system would have many benefits for the Player. We would have realistic situations at the Frontlines. Often Airsquadrons with not enough Planes, because the factories got strategically bombed since years...and only a few Planes reach the Front lines. Same could be done with Tanks...and even Infantry units. Factories would Produce Military Equipment, like it was in Vicky1. So a Nation like the SU, could pre-produce big amounts of Equipment...and when the War brakes out...and a sneaky German Invades...they could do then a rush in Division Production, with a Basic Training, that needs only 1-2 months to Produce the Unit, and fill them easily with the 30,000 pre-produced Panzers.
The disadvantage of produce masses of Material to soon, would be to give the new trained troops obsolete Equipment. You could also easily sell Planes/Tanks/Soldier Equipment to your Allies. Land lease would make much more sense. WHen a submarine sinks a Transport, then you would really lose the 100 Planes, the US send to Russia as Land Lease.
That new system would also force you...to not only research new techs, you also have to build it seperatly in your factories..and then equip your units with it. So we wouldnt need any more the slider for "upgrading". This would be now managed directly over the Factories.
Now think about, you have a nice brandnew "Focke-Wulf" factory in Dresden. YOu would then defend it with best Anti-Aircraft Units..and many squadrons of Fighters....to stop the british Bombers to bomb them down into parts. Oh, and factories would produce Planes/Tanks/Soldier-Equipment also faster and cheaper over time....as long as they produce the same tech. Now you will think 3 times before you change your BF109D factory into one that Produces Focke-Wulfs, or even HE111 next. They would need a year maybe until they are as fast as before in spitting out new Planes. That would force Players to use older equipment, even if they have researched newer/better one. This would simmulate the fact, why the Germans even 1944 still produced BF109´s. Same for Tanks and Soldiers. To simulate History, a german player would more often change the produced units....has then hightech in the field...but at much lower numbers....as a Soviet Player or a USA Player that mass Produces older Tanks and Planes but in gigantic numbers.
How about a german Player that adopts this strategy and massbuilds 109E´s even until 1945....but with much higher output. Completly new strategic Decisions for a Player would be here. I bet most of us would like it.
The question is: Is this doable in an Addon? Or do we have to wait for HoI4 for this? I personally would love it, to produce all my shiny planes with my hands, having complete control over it. Would love it to build a new TigerII-Factory in East Prussia...and massproduce this babies in thousends. Or build a U-Boot-SHipyard in 1936 at a baltic Harbour in germany. After 3-4 years...i would have a high-modern shipyard (beside the ones i start with) there that will produce the masses on Submarines i need to kick the UK out of the war soon.
For the devs: I dont want a complex Factory system like in Vicky. A simple would do it for this idea. Sure, the Production would need Ressources, maybe even MP to fill the factories and/or Officer Points. I think it is doable for an addon. At least i hope so.

I dream about that since i heared, that HoI2 is planned.