(Hypothetical) West Germany v. Mujahideen circa 2009 CE

[Imp]

Players should note that body armor would have a serious effect in playbalance, making armies with those nearly invincible, Like T-54 x M1 Abrahms(even early ones)

From what I understand would have as much effect on the game as troops wearing a beret or helmet as in none. If lucky & a glancing blow may prevent an injury otherwise just reduces the level of. Reasonable measure of protection vs shrapnel but like helmets that bullets most likely going through it, cost comfort as in weight & climate allowing wearer to operate effectivly all restrict it.
The tank analogy would be decent ammo storage so it does not go bang once penetrated.