Out of all the units the M8A1 and m14a1 on the move suppression are probably the only things that might have to be looked at.
Putting AP and incendiary on the same level is a bit odd. One does +100% damage and the other 25%, the former reduces the reload duration by 50% while the latter does not and requires a lot better foresight and timing. I leave it up to you to figure out which one is which, the buff in penetration is about the same (9 vs 10). This ability is such a non issue with its near negligible effectiveness against infantry that probably no one would mind if it was moved to vet 1, but it's not an ability that ever overperformed. This is a call for homogenisation, which I am fine with, but it is not a balance issue.
Now take into account the armor values of Ostheer light vehicles and allied vehicles and you will see that 0.5 can easily counter them at vet 0 while HMG-42 need vet 1 and HMG-34 has a hard time even at vet 1.
This not a simply case of homogenization. The 0.50 was designed as a light vehicle soft counter because it was expensive to get both 0.50 and an ATG, now that is no longer the case and there is little reason for vet 0 AP round option.
It is conveniently ignored that the difference in armour between the m20 and 222 is small (9 vs 11) and that the difference in health is a lot bigger (240 vs 320). This again is not a balance argument since the m20 has not been an issue ever since it was nerfed, this is another, surprisingly, call for homogenisation where two very different units (one effective against infantry and light vehicles the other only against infantry) are compared, all differences ignored and then the difference in armour picked out because they both have 4 wheels. The smoke argument is odd, since all light vehicles (that have it) get smoke at vet 0 (the only exception being the m8a1, which is a t4 unit). Personally I'm all for locking it behind vet 1 for all light vehicles.
Again this is not a homogenization issue, its about a unit performance according to its cost and tech level.
You conveniently ignored the fact that m20 and 222 have different tech cost, different costs and M20 can buy armor/HP, increase the gap in armor and decreasing the gap in HP.
And what are those all light vehicles that have smoke? the AAHT that can not fire on the move?
Or the Puma/AEC who become available when ATG are available and cost more the 3 times the fuel?
The 222, 250, 251, M3 , M5, WC51, Grayhound and UC do even have smoke, why should the M20 should have? So it can drive in front of HMG and create a smoke screen and give even less reason to USF user to unlock grenades?
I do agree with the m5a1 that it could potentially lose its on the move suppression. It has to be seen however if its performance needs adjusting after the change.