Firstly i never stated all usf units are nerfed to the ground although some are.
And that is direct result of the US tech revamp which was faction buff and changed the original design of the faction. Actually I had pointed out it at the time.
And you almost never see the m6 because people rarely build the m20. Or i must be blind.
Saying that m20 has been:"nerfed quite a bit over the years" and m20 is not a very common sense is not nearly the same thing.
I am not sure what mods you are playing so I respond to why you do not see it.
Anyway I think we can move on.
And here are the other buffs m20 got that where missing:
"M20
The m20 has received some adjustments, as it would have arrived even later, and been even less effective within this new tech structure.
Manpower cost from 340 to 240
M20 accuracy from 0.75/0.475/0.2 to 0.55/0.45/0.25
Weapon accuracy increases with veterancy: +10%/+15%/+15%
Veterancy requirements lowered from 880/1760/3520 to 500/1000/2000
Veterancy 3 reduces time to plant mines by 5 seconds.
Veterancy 3 increases stealth detection by 10; 35 stealth detection radius from 25"