Still there 2 different systems different armor types may offer increase protection from certain weapon, one needs to use target tables to make weapon cause more or less damage to different targets.
Complicated system are not need when there easier solution.
To be completely honest, I don't agree that having infantry armor types are necessarily the complicated system.
For example, to me reading through the history of these forums, it seems like a lot of weapons/vehicles/teamweapons were garbage at what they did or completely oppressive.
I think that infantry armor type did lend itself better to "Rock Paper Scissors" type gameplay where it's less effective to cheese and spam units.
Like in Kurobane's example where mortars did more damage to teamweapons instead of infantry squads. Imagine how much time could have been cut from balancing the game if instead of having to balance a unit around its damage being equal against every single other unit in the game, the damage could have been fine tuned against units.
If, for example, the 120mm mortar when it was an insane wipe machine, had its damage reduced against infantry but kept high damage against garrisoned and teamweapons out in the open, how much of an issue would it have been?
You cannot spam it as easily because it's not as effective against enemy infantry any more.
I can see the merits of infantry armor type.
The Infantry armor system may have been complex but it was better for overall balance.
...Infantry Armor prevents [random rng] by allowing units to be counters to specific units vs doing generic damage vs everything. Coh 2 mortar could do 100 damage for example, and it would be the same regardless of what it hits while in Coh 1 that mortar would do 100 damage to Machine Guns (the thing it was meant to counter) while doing 50 damage to a 3 man squad, and 75 damage to a 4 man squad. Basically it prevented more BS than the current system
Like I said, I can see the merits of infantry armor. It's just that it needs to be communicated to the player somehow.