While searching for such a modern day mod I ran into this thread https://steamhost.cn/steamcommunity_com/app/529340/discussions/0/3826410044362941824/?ctp=2 on the General board and thought I'd make a thread with what my reply would've been to the OP to avoid gross necromancy and maybe help get such a modern day mod:
The OP states their mod dev team wanted to go down to the dollar/person in terms of granularity but the game engine doesn't allow it intrinsically because of 32 bit limits for values. While I understand why the dev team in question tapped out then I have to question why they wanted to go that deep because while 64 bit makes sense for proper simulations a game is never going to be one in any real way (trying to simulate an economy will make a CPU have a stroke if you properly model it from a both macro and micro scale, trying to do that alongside, for example, simulating combat even down to the platoon level (lets not go squad or even soldier), population migrations, population interactions between each other, criminality, corruption, etc,etc, etc, would make my Zen 4 12 core just straight up freeze in the 6+ billion pop level a modern day mod would want to do if it's going 64 bit and sim hard. So a level of abstraction isn't just needed, it's critical to not turn the game into "But can it run Vicky 3 Modern day mod?" levels of hardware memes. For this reason I would encourage any modders discouraged by posts like the above linked one to review the possibilities in terms of abstraction from that perspective and find middle grounds between realism (sim) and practicality for people not running the game with a quantum CPU crunching most of the sim numbers and their regular PC doing the game graphics bit.

Like off the top of my head (Layman though so donno exactly what could be possible mod wise):
Modelling things for populations in the 10k unit range for abstraction on the strategic level and if there's an option for it in modding, have battlefields include civilian pops in the area estimated from local density with different minimum size for it so you can model the messy business of civies in like villages getting stuck on the sharp end. For economies, as someone mentioned in that thread, while the US is in the tens of trillions range and other G7 countries aren't slouches either, most of the other hundreds of countries around won't be so determine in the design phase what would be the smallest economy possible (say a breakway state like Transnistria going full independent) and set the values for that to be adequately simulated as the minimum values for abstraction (GDP of Transnistria for anyone curious is 1.2 bill, approximately and still field, relative to their size and neighbors, a respectable army within that tighter than sane military budget) and scale upward from there. For culture, literacy, anything else like that, again, find the smallest country those would be relevant for (I'd assume Vatican City here off the top of my head but could be very wrong), set the minimum to where the simulation would work with it and go from there. It's doable without going insane on sim and hugging the 2.1 bil 32-bit limit like a very passionate lover or reducing the game down to unrealistic scales (or wishing you could melt a PC to slag with a 64-bit, full phat, Aurora 4x eat your heart out, life sim).

PS: I suspect the devs put the 32-bit limit more to avoid modders trying to chase the dragon's tail sim-wise more than malice or complacency as when you think about it a lot of us don't ask if we should, we only check if we can and if that leads to someone's PC dying spectacularly due to overheating on a famine event in, say, China then that's not the modder's problem (and you can bet the bro who's PC is now glowing red will ask Paradox for compensation as again, he never asked if he should try running that level of simulation on a poorly ventilated PC from the mid 2010s, only if he could which he could, for about 30-40 minutes).