Sorry for the huge amount of errors
i think this is suited to even take part from the coldwar to the modern age. So u start in the year 1947 as lets say the United States. You are the leading power for the capitalist and democratic side of the world while the Soviets are ur enemies. There can be things like proxy wars (just like in our history) where the US and the Soviets fought kind of "indirectly" to gain power spreading their influence across the world. Situations like the Korean war where it still remains north and south or the vietnam war where north and south also fought. The cold war is pretty much a constant fight between US+Europe against Soviets+China. And u can see that today. This is why I think mixing in both of these eras can be very entertaining because today its the same, US+Europe (mostly UK, France and Germany) against China+Russia with some joiners like Iran.
But i also think the cold war concept can be a whole different title because it just has so much to it now that i think about it
So this is kinda how it goes, I think this 1947-2020 period can be split into 2 games, the cold war with the struggle for power and ideology and the modern day with the struggle for supremacy and resources and also economy and the struggle to keep world peace a reality. U guys can decide which u want, a combined game or 2 seperate title ideas so ill do both seperate
Cold war era
This was a very vast era so there can be a crap tonne to cover.
It can all be based around the struggle for an ideology unlike hearts of iron where it was the struggle for an alliance and factions. the 2 we can call them "factions" are Democracy or capitalism vs. Communism or Socialism. This game can introduce new mechanics like propaganda which was highly used in the cold war and even during WW2 but it wasnt tapped in 'HOI' so it is kinda brand new. For the majority of the game it can be US and Europe vs. Soviets and China and the game can be based around influence and power around the world. For example the Korean war where after WW2 Korea was split between the US and Soviets and they fought for years before ending in a stalemate. The vietname war where North was once again communist vs the south who were democratic. The soviets and the US always intervened around these wars aand were always involved.
The game could also consist of other very important factors like economy and technology.
For economy it was one of the factors that actually collapsed the soviets and technology was always the fight of power between the US and the Soviets.
Things like manufacturing and goods producing can be big for winning power to invest in research and technology, well that was kinda the biggest player for power among the two ideologies. Things like the space race could take place which if u win could give bonuses and maybe have a humiliation mechanic which humiliates the other ideology. Then u can impliment kinda like a prestige system like in EU4 but instead its more a global prestige rather than a national prestige. So this can be a meter where either the Commies and Capitalist nations can fight to get themselves higher on the bar based on what advances they make like the space race or nuclear arsenals.
Nukes... Nukes are gonna ofc be a big part of this game. Like the space race nukes were a huge symbol of power and this kind of cold war game will allow for even a Nuclear war! Nukes in ur arsenal could also effect this global prestige meter to show who is the most fearful superpower in the world!
But ofc advancements in the military in general are also important as if ur fighting a proxy war or even the leading superpower straight on u need a powerful military. But ofc paradox games are known for making history into ur pupppet and taking ur own path so many things can be implimented like turing the soviets democratic and fighting the chinese or turning the US communist and making them invade Europe or u can even bring fascism back and rebuild the Axis. The game can also make the puppet mechanic more dynamic than HOI where u can use them to actually gain wealth or fight wars for u to spread ur influence because all in all, the cold war was all about the Soviets and the US being puppet masters to prove who was the strongest.
This could lead to a different alternative like what if the Soviets didnt only stop in releasing sputnik into space but actually colonized the moon before the US or what if the Soviets were the ones with the better economy and the larger influence forcing the US to collapse instead in an unknown wat, maybe into all their states as seperate nations or just releaing texas or something or just stay normal but all their influence is gone but this will ultimately be the end of the game because this is how the cold war ended, with one of the ideologies being defeated
Now for the Modern idea
The moden world can be vastly different. With the collapse of the Soivet union in our time or maybe some linking can happen between the two games or one game whatever, and the Us can collapse instead, the world enters in a darker world where the consumption demand is greater than in the cold war and resources are dwindling. This kind of concept can be based off of economic superiority and military superiority. The US and China and to an extent Russia are all fighting to take the seat of power in the world where u can introduce mechanics like population but make it more dynamic than Vic 2. Things like health, consumption rates, taxes and jobs, interest and inflation and the holdings of important resources like oil in the middle east. It also gives lots of opportunity for many regions to be important. So if u want a good game the game isnt centred around the superpowers only but lets say u play as Saudi Arabia, u can control the oil distribution to other countries and become an economic super power while trading as little oi as possible away. Maybe u can even do things like freeze the oil and save it for war.
This game would be bug on 3 categories, politics (who controls the most power in the world and who is a force to be reaconed with), Economy (how wealthy ur nation is to advance urself to be able to invest in more things like research) and military (kinda like the US today where they have the military superiority to appear at ur doorstep with a 600 billion annually invested army! And this allows them to control how oil is traded, thru the dollar). The modern concept for a title should be based on power in these 3 categories and if ur leading in all of them then ur probably not going to be defeated. But that's the challenge. Many things can be introduced lke colonizing Mars, Nuclear Fusion, Railguns and advanced weaponary and if u play as Iran, secretly make Nukes

DD.
I think a game like this can be really fun, especially that Iran part, there could be a more dynamic espionage system where u can fight not only through a military but through cyber wars and shut down electronic military weapons like batteships so u can just march into the country. This could be very fking fun because if u have power like this and u play as idk North Korea u cant face the US army head on. So invest into EMP nukes or cyber spies to shut down electronic military weapons to get the uppwer hand. This kind of mechanic could make the whole idea of conquest in a paradox game not only about the bigger or more equipped army but a whole new battefield.
Ofc these are only brief ideas and there are many more things that could come in. I dont see a problem with memory and how the game(s) run as thats the beauty of paradox games, most dont even reach 4 GB. Eu4 is what, like 1.8GB-3GB or something and look how expansive it is. Since paradox games are 32 bit and not 64 bit the gamplay possibilities are much more possible when graphics isnt the most important thing in the game
If u have any suggestions on my post feel free to post urself