You can’t do that in War Thunder.
In this game, tanks don’t operate in the contexts they did historically. They don’t fight in an environment where they’re engaging soft targets most of the time. They’re not performing a doctrinally assigned role as part of a wider organised unit. They’re not even fighting historical armoured opposition.
As if that weren’t enough, plenty of soft factors (visibility, reload speed, reliability, mobility on rugged terrain) are equalised in WT.
This is a shooter game that uses tanks instead of infantry. If you choose it as a correct historical representation of a given tank as a physical object, it’s hard to do better. If you choose it as a correct historical representation of the employment of tanks, you have made a terrible choice. And a tank class is a direct product of its intended employment.
Btw, as others have pointed out, standards are incredibly inconsistent across nations and decades. Britain had cruiser tanks and infantry tanks, and later universal tanks.
While the Germans had regular and heavy Panzerjaeger detachments, the Soviets never differentiated between tank destroyers and SPGs - every crew of an SPG had to train to perform indirect fire and infantry support missions, but were also instructed that if tanks appeared on the battlefield their first job was to destroy the tanks.
Italian nomenclature is just that, nomenclature. It was an administrative holdover from the mid 1930s. Bureaucracy. No one in their right minds dreamed of using the P40 as a breakthrough vehicle.
Even when things are relatively uncontroversial, “history” often complicates the picture. The Tiger I and the Tiger II are heavy tanks. So… are they breakthrough tanks in the classic sense? Well, the first Tiger especially relative to its time of introduction arguably has some genuine breakthrough traits, but these vehicles arrived when Germany was already on the defensive and they were mostly used as ambushers or, really, to shore up the firepower of Germany’s depleted infantry. And in game, they certainly both play very differently than a Jumbo… so what do we call them?
Is the Panther a heavy or a medium? The Soviets considered it a turreted TD… it certainly doesn’t look like the type of machine that excels at exploitation missions. The M26 has already been brought up too.
For the purposes of the game, the classification they have makes sense. It’s fine. The only tank I genuinely don’t understand the classification of in-game is the Caernarvorn.