I don't want grens and rifles to have the same stats in different uniforms, I just want grens to be able to keep up with rifles early game in some way
That is the problem on faction design level, which will not be able to be fixed without overpowering grens. Or...?
USF have just RETs and rifles, they have locked up support weapons, which means they can't rely on them, they are forced to use basic infantry and nothing more, because they have nothing else.
Wehr on the other hand have access to various support units from the get go, plus these support units are most cost effective out of all other armies.
Grens simply can't keep up with rifles on the army design level for the sole reason of amount of tools they have at their disposal at this early stage of the game.
It boils down to field presence and I actually believe that this issue could be fixed by NOT giving USF squads for teching and instead leaving them as optional purchase, just like you have to re buy them after they get wiped.
As a result, matchup of USF vs OKW would be grossly imbalanced towards OKW, which again could be counterbalanced by stripping shreck/nade package as well as free truck side benefits(medics, rep pios, aa gun) to the tech and locking them behind side costs.
This way OKW wouldn't be as overpowering against brits, who would have more room in the early game, nothing would change vs soviets(except for the side costs for OKW, which would slow them down a bit if they wanted to get everything, not much to do vs sov T2 and cons can't pull it vs volks anymore), except OKW would now need to choose if they want early shrecks or early luchs, USF would have lessened field presence in early game while closing the army cost gap for early and mid game vs ost.
There, everyone is happy.
just like I want USF armor to keep up with Tigers and Panthers late game. You don't have to copy and paste units to do this. But creating factions with a more equal balance of power at each game stage should help balance all game modes.
This part we have pretty covered as well, zookas or USF AT guns alone aren't most effective things, but combined with themselves as well as with jackson support, USF have means to fight all armor except KT and JT.