You have historical facts on the bulletin descriptions.
Gameplay needs to be healthy.
Yes, but all that can be done also being realism. Imagine this, german grenadiers would not be as good as conscripts, because 6>4, however german MG 42, would be much better than maxim. That would encuorage less spam and combined arms. Maxims would still be built, they would still suppress infantry, but deal overall much less damage than the mg 42.
T-34/76 would have more armor, but a considerably less powerful gun than a PIV, and the panzer IV would scale better, due to having a big armor bonus at vet 2. VET 0 PIV is the G version , VET 2 PIV is the H version with upgraded armor. All in all, these vehicles would be mostly equal, with the panzer IV having some slightly better features (extended vision range, pintle mounted machine gun, good scaleability because of vet 2) while t-34/76 would have overall similar stats however be much faster . Something like this for fuel cost 110 for t-34, 120 for PIV. Overall these vehicles would be quite equal, but also much different at the same time.
However, germans would have the STUG, which would have more armour than the T-34, a better gun,and HP buff to 640. but overall would have a big minus, lack of a turret.
The t-34/85 would outclass all of these vehicles, however, the stug could still go toe to toe with it.
And of course panther would easily destroy a t-34/85, and be more or less comparable to the IS-2, with panther being mostly equal in AT power, however IS-2 would have a slow reload,making it less good in tank fights, however would be perfect for anti-infantry duties. and panther would have decent anti-inf, (slightly less than say, a PIV), overall IS-2 would still win vs a panther, however, panther would just be slightly more expensive than a PIV, say, 150 or 155 fuel and IS-2 would be a very expensive 240 fuel tank.
The tiger would be somewhere in between the panther and the t-34/85, somewhat better than the t-34/85 in terms of armor and firepower and AT power, but not as good in mobility and cost. While the panther would beat the tiger in terms of armor, AT power, speed, but lose in anti infantry firepower. After all, the panther should be overall better than the tiger, why? Because of high tech cost of T4.
ZIS-3 could have it's barrage for free , however, penetration would equal the t-34. Pak 40 would still retain its very strong penetration, TWP would be fixed. So in the end, zis-3 would not be very effective againts againts heavy armor, but rather be a good artillery piece + decent AT. While PAK 40 would still be quite effective againts all tanks, and possible only struggle somewhat againts IS-2.
The su-76 would simply be a ZIS-3 on wheels, with 400 hp (not the 320 hp it has now), and su-76 should have direct fire effective againts infantry, however it's range nerfed to 50.
SU-85 would just be a t-34/85 without a turret, so it would come cheaper, t-34/85 would cost 140 fuel, su-85 would cost say 120. 50 range, same as a panther, stug. However it would also get the AI performance of a t-34/85. It's mobility would also be buffed. Of course, big minus like the stug, no turret.
Or to be honest, scrap the whole shitty idea of tanks having different ranges. All tanks and at guns = 50 range. Only exception would be isu-152,elephant,king tiger,jagtiger
Everything can be balanced and ALSO realistic at the same time, you just have to think and it will work.