It's a fascinating read.
Right, so what do you suggest?
A streamlined OOB, perhaps? Something where divisions are automatically assigned a commander, and where Lt. Generals, Generals, and so on can only control X amount of divisions/brigades/units? Perhaps a mechanic where we assign a single commander to control an entire theatre and where that commander's bonuses apply to all the units assigned to that particular area? Nation-specific OOB/organization mechanics? Germans get a special Kampfgruppe mechanic after researching the land doctrine tech where a new "army" of X amount of divisions gets a short boost to its combat effectiveness and planning speed to reflect the ad hoc nature of the formation?
How about supply? Looking at HOI4 as it exists now, how would we add in a better supply system that isn't already rendered redundant by the infrastructure mechanic working in tandem with naval bases? Perhaps...dedicated supply depots that are constructed using CIC that can be built in currently occupied land and where these depots give a significant boost to supply in that particular area?
Okay, fuel. There's a strong link between rail transport and fuel, and we all know what happened on the Eastern Front with the railroads, not to mention Allied bombing of rail systems on the Western Front to disrupt German logistics. Okay, how do we model this in-game? Perhaps we change infrastructure to 2 separate mechanics, where we have dedicated rail systems along single provinces that can be deliberately targeted by air using new air mechanics that would enable player to choose if they want to attack MIL factories, CIC, or general population centers to act as a mix of infrastructure destruction or apply a small (and I do mean small) debuff to National Unity overtime? Now we would have dedicated rail mechanics to act in tandem with overall region infrastructure, which might help.
This forum and these discussions are often too far removed from the actual gameplay mechanics we have facing us right now. I think a lot more constructive work can be done in these discussions if we try to ground the conversations in the actual game we have with us, not the mythical game some people want. I think this thread could help by grounding overarching, theoretical discussions in terms of actual gameplay mechanics.
Edit: This might not be the best thread for this, actually. Sorry!
First of all, sorry for spamming, but there are so many comments I want to answer that I lost overview and I thus need to do it in separate comments. Please forgive me, forumites and mods
I normally enjoy discussing game mechanics on a deeper level, so I'm going to do it, no matter if it belongs here or not.
For me the OOB system would be a hybrid between 3 and 4. Leave out the divisional commanders, as they really are just annoying to assign and you don't really care about them. Instead, I would say to introduce a more in-depth system of staff, having a commanding officer and his chief-of-staff for corps and up. They would then have different functions, traits and capabilities. Also, instead of having leaders, divisions can gain traits for different accomplishments that would give them boosts for different things. Additionally, I think facilitating or just completely leaving out on-map HQs would be best.
For supply, I would just add in two more "equipment" types, general supplies and fuel. Each unit on the map needs supplies and the motorised ones need fuel(including ships and planes). And like in the old system, the fuel and supplies would be transported over the map individually, as well as the needed equipment now. Of course the old system was flawed in some points, but nothing that could not be fixed, and some of the oddities could actually bring in some flavour. Want to launch an offensive in the russian steps. Awww, too bad that we couldn't stockpile enough supplies and fuel and now we are stuck after one province. Such things happened in real life and should also happen in game.
I still feel however that, if the player wanted to take over some control it would be great to give a certain amount.
Creating supply hubs or adjusting supply priority to certain units of the OOB would be great already.It would help steer the supply in the right direction. It would also be interesting to see what happens, when you let the supply run along the chain of command, meaning the supply running from HQ unit to HQ unit until it reaches the divisions.
It could be possible to stockpile supplies with the divisions preparing for an offensive, which would result in them sucking in all supplies from multiple surrounding provinces. The amount of supplies and spare equipment they can stockpile, depends on the size of their supply unit that is attached similar to a support battalion. This would in turn need more manpower and also trucks or other ways of carrying supplies. It would also mimic the Allies in the late war for example that would be masters of logistics, but also have a huge amount of material and manpower engaged in it, quite opposite to the Germans, who just couldn't do that, and therefore even worsened there already bad supply situation considerably.
And of course also introducing some kind of rail system you suggested that would be on a single province basis, would be fairly high in volume of supply throughput, but would be very costly to build. Also it would not be able to supply the troops directly and the amount of supply that a division receives still depends on the infra.
I guess those are some basic ideas on how the game could be a lot more engaging and also a bit more challenging.