Honestly thought of lvl up infantry but it's so hard cause of the weird stats in game....
Like one example is the SMG which one officer makes US and Soviet SMG a menace against buildings.
I do have another idea which is the conscription.
It can be toggled on and off through techs and would allow to toggle the normal rifleman vs a conscripted rifleman. Conscripted rifleman will have significantly more HP while lower damage all for the same cost.
Can only build
Trench
Barracks
Medic Camp
Bunker
When "CONSCRIPTION DECREE" is researched, rifleman in training list will be gone in exchange of conscripted version.
Another tech would become available which will be called "Back to normal"