How would you depict asymmetrical warfare in a strategy game? Doesnt need to be in HoI4, just in general.
Combat Mission: Shock Force 2 and Radio Commander portray asymmetric warfare of two stripes;
CM:SF2 portrays the modern, full-spectrum dominance of the late 2000s United States military invading the outdated, outgunned, untrained conventional conscription army of Syria. The US Army is invading through Route 2 from Iraq, breaking past Al-Tanf and heading to Dimashq, the USMC is landing on the coast, and NATO forces are invading southwards from Turkey on Aleppo. The Syrians are going to lose no matter what, and so the goal becomes to make it as painful as possible. Syria, outside of the context of a US/NATO invasion, is not weak; she has relatively modern version of late-Soviet armor in amounts that you wouldn't balk at, with the majority of troops being equipped and trained to Soviet standards of mass-mobilized mechanized forces. Unfortunately they also have a dictatorship more concerned with internal stability of the regime than an actually effective military, and so training is poor and the paper-strength is far below reality. Everything is centralized, so only commanders can call in rare artillery strikes compared to every US squad being a potential forward observer team. Air cover is nil and mobility is nil as a result despite the amount of tanks, APCs, and trucks. Eventually it all falls apart and a low-level insurgency of the remnants and those taking advantage of the power vacuum begins. IEDs, technicals, etc, start to appear. The Syrians are essentially aiming to delay at all costs versus a force that knows where they are at all times and can shoot them accurately from beyond their own range, even though they are a conventional force.
RC portrays, instead, the position of a commander from well behind the front in a tent relying on US Army radio communications to decipher the battle space during a Vietcong insurgency. It's more a puzzle game than anything else, but you have air cavalry, heavy artillery, tanks, etc, at your disposal against light infantry using the terrain and small, isolated teams to their advantage.
The issue is that you are either playing as the operational winner (the conventional, advantaged force) or you aren't having fun. To have fun as the Syrians in CM:SF2 you need to be a glutton for punishment and accept failure as the best outcome possible. It's difficult to portray beyond "you lose" because that's reality; the Vietnamese didn't defeat the US military, the defeated Congress' attention span after the '72 peace accords. The Jugoslav partisans didn't defeat the Axis powers, they found a country empty in 1944 as the Germans abandonded and were abandoned by the Balkan allies. The Mujahideen did not defeat the Soviet Army, they defeated an unsupported Afghan government which was abandoned just like the AVRN after a Soviet drawdown, not wanting to spend more money on a pointless conflict. The real standout here is that you don't win by skill, strategy, or any actual achievements besides longevity and sheer survival. The goal is to do just enough to make it more expensive for the enemy than $0, stretch it over enough time to get eyes and dissent, and then have enough strength in the drawdown to topple the remaining government and be the strongest group left. That's not fun in terms of gameplay and is not represented well in abstract like the operational focus of PDX games. You can really only portray realistic tactical engagements or super abstract strategic level stuff, like hiding in Qatar or Laos until you can topple the PLO or AVRN. It's also incredibly difficult to portray how often the "victor" doesn't win because they end up fighting a civil war; the Viet Minh, Mujahideen, Hamas, Greek partisans, Ukrainian People's Army, Libyan rebels, etc, they all experienced significant insurgencies or civil wars against themselves after coming to at least nominal power. Many were victorious but it still took years for the final shots to ring out.
A decent portrayal of asymmetric warfare is either going to be more abstrast than HoI4's naval system, or it's going to be about seeing 90% of your men die in a random helicopter strike attack, then fighting in Jeeps against tribals in Toyotas.