As far as I can tell, any game of the post-WWII era would be best served by completely new mechanics. The Cold War isn't just nukes and space programs on top of tanks and Communism.
That being said, most folks tend to forget that each of Paradox's major franchises are different kinds of games. Ignoring their historical periods, they have radically different focuses. CK2 is all about dynastic politics and religion and individual characters. You can have a perfectly fun game being a power behind the throne in a huge empire without stepping up and taking it yourself. Sometimes more fun, depending on the empire. Hell, CK2 can be the Paradox game that is most fun to lose.
EU4 is about painting the map and trade. It's got all kinds of nuances, but at the end of the day, it's an empire building game. EU4 is the only game made by the studio that focuses on exploration and controlling trade (not just controlling economic activity). Even merchant republics in CK2 are small potatoes compared to trade in EU4.
Vic2 is a game of economics. It's the only Paradox game where the amount of coal available in the world can literally enable economic growth or strangle and kill the economy. Empire building is important, but the smart players are less concerned with map painting and more concerned with conquering POPs and specific resources. But, aside from all that, Vic2 is also a game where dominance can be achieved through smart internal management much more so than any other game in the portfolio.
HOI3 is all about the war. The only thing that matters is winning the war. The long term repercussions are irrelevant. Impoverished your people for 8 years? Doesn't matter. Spent 4 years under partial German occupation, only to turn it around liberate everything from Moscow to Paris? Doesn't matter. Conquered China, but got nuked and occupied at home? Doesn't matter. Exhausted your manpower pool completely fighting to get to the last 20 miles towards Berlin for a German surrender? Doesn't matter. In Vic2, fighting a lengthy war that wipes out tons of manpower will have consequences you feel for years that will be unpleasant. In EU4, betting everything on a war right now that you barely win results in your enemies taking you apart later. In CK2, winning the current holy war is meaningless if your genius ruler is killed in battle against the infidels, leaving his clubfooted imbecile son in regency, with half your titles handed out to your other sons in gavelkind (because you didn't sort it out before dying), and your treacherous uncle is the regent, refusing to approve anything that would help the realm while revoking titles via plots and lowering crown authority.
If I were a game designer working in Sweden, I'd say to myself, "What new kind of strategy game could I make, that could still use some stuff from the current iteration of Clausewitz? And what historical era could I place it in?" What I wouldn't do is say, "Alright, let's crank out a Cold War game and just use the same gimmicks from HOI."