Edit: Disclaimer! I don't think that any of these modifications to the in-game tank are probable, possible, or necessary. Buff My Tank segments are for entertainment purposes only. -EE
The T-34 used to be a solid tier 5 medium tank, but premium ammo for credits left it in the dust, behind the 105 mm howitzer M4 and PzIV crew. Let's see what historical resource exists to bring it up to speed, through the current power creep.
First, the gun. The ZiS-4 is really the only choice as the "top" gun on the tank, and the Chinese iteration admits as much. The alpha on it is pitiful, so the peek-and-poke (for massive damage) playstyle of other swift and unarmoured tanks (pretty much every French tank comes to mind) does not apply. The slower loading and harder hitting 76 mm guns increase alpha by a tiny amount, at an unacceptable cost to every other stat. Since many tanks in the game get guns that go anywhere from just being mentioned on paper to absolute fiction, why not give the T-34 a gun it actually was tested with, the 85 mm S-53. Sure, the reload rate would be slower than the same gun on the T-34-85, but a different playstyle would be viable. Or, maybe, the T-34 could get a derp gun of its own. A project for a 120 mm breach loading mortar using the F-34's recoil system existed.
Speaking of the gun, the Soviet developed a vertical stabilizer for the T-34 (STP-34), T-34-85 (STP-S-53), and M4A2 Sherman. If vertical stabilizers were based in history and not in balance, the T-34s would get one of those (as well as the M4 and T-26).
|Diagram of a T-34-85 vertical stabilizer STP-S-53|
|T-34 with additional armour. From Amour Protection of Medium Tank T-34 1941-1945, Postnikov.|
|Images of the T-34 with commander's cupola and T-34S, from Soviet Medium Tanks 1941-1945, Solyankin et. al. To a casual observer, these tanks are indistinguishable from the T-34 Model 1942.|
In game, the bonus to the gunner would lead to faster aim time and a more accurate gun. The commander would give larger view range. While the loader's cruel fate might reduce the ROF just a bit, a T-34S crew layout would turn the T-34 into a capable sniper.