I should preface this point by clarifying that my perspective does not include Rank V firearms, as I recognize their necessity for the overall balance of that tier, and I support their current implementation. While the tanks at this rank are generally well-balanced, the lineup relies heavily on rare firearm models.
My main argument focuses on the many mass-produced tanks or guns at lower battle ratings. Take the SU-76M, for example—it was the most widely produced Soviet tank destroyer of World War II. Logically, it should be placed in the Silver Lion research tree, just like the Marder. However, due to early game design decisions, it remains a premium vehicle. The same applies to the StuG III A, LVT tanks, and many other vehicles, whether aircraft or tanks.
These are not rare prototypes like the Maus, which had only two units built, nor are they tanks with production runs in the mere hundreds (three-digit figures). These mass-produced vehicles could and should be fully integrated into the standard tech tree.
As for the premium vehicles they replace, they should be given functionality similar to War Thunder’s “Talisman” boost—purchasing them should at least grant a permanent credit earnings bonus. I am aware that Digital Forms (DF) is already taking steps in this direction, such as with the Jagdpanther.
I sincerely hope DF can accelerate the implementation of these changes. The current pace seems somewhat slow. My suggestion is to reintroduce more of these older premium vehicles but distinguish them with unique identifiers, such as adding designations like “1./Panzer-Abteilung 205” or other unit names, rather than merely compensating owners with a cosmetic skin that makes the two versions nearly indistinguishable to outside observers.