If you want accuracy, you would need to introduce the concept of units ‘breaking’ and running before they are destroyed. Squad Leader (Avalong Hill 1977) had this, some squads keep fighting when they are down 50% strength, others ‘break’ and run when damage hits 10%. Of course each of the existing units when they need variable strengths compared to other nations units. This would require a switch to dice with a greater range of values, I’d say minimum 10 sides, but lets use 2 10 sided like AD&D. No way a soviet or german tank unit fights the same way as an allied unit. The way the allies fought german tanks was using a squad of 4 allied versus a german tank. It starts like this, the first allied tanks lights up like a torch and the remaining three start to manouver around the german as its turret rotated a bit slow. So, allied tank #2 then #3 light up in flames and the 4th allied tank gets in behind the german and lets loose at point blank range in the poorly armoured rear of the German and manages to disable it.
New units would not fight as well as vetern units of course so you would have to keep track of the age of each unit then modify its combat values based on just aging and also exposure to combat. Yeah cool, way more accurate, of course each countries turn would take a few hours and we would have to go back to cardboard units with the 3-4 % values representing the units abilities. We would need zillions of these units for each combination of values.
In ‘set-piece’ battles the Japanese were getting slaughtered against the US. Perhaps it because by 1943 the US was producing as many machineguns per month as the Japanese produced during the entire war. I think the Japs having never faced trench warfare and the futility of charging into massed machineguns had no concpet with this type of warefare. Moreover, the Japs never seemed to retreat so they had little ablity to learn lessons as nobody came back to HQ with information on what they faced. I would think for accuracy this would have to be represent also with different strencth units.
Personally, I think AA has found a pretty good balance of accuracy and playability.