Yak-9T - incredible firepower (or maybe incredible tank's lack of armor?)

[gaunt1]

I think it would be more or less simple to do it, there should be a difficulty option:
1, arcade mode: no change, everything stays as is now.
2, realistic mode:
7.62 could destroy unarmored vehicles only
12.7mm effective up to APCs. All tanks, including light ones invulnerable
20mm, same as 12.7, but small chance against light tanks.
23mm, effective up to light tanks, small chance against medium. Heavies invulnerable.
30mm, effective up to medium tanks, heavies still invulnerable.
37-45mm, effective up to medium, small chance against heavies.
75mm, kills everything easily.