They perform ok, but NOT in the first min of game. Give them worse start weapons, old weapon profile with a 30mun mun upgrade.
After that we can balance Cons, Maxim etc.
When first penal arrives, you have already 2 mainline inf squads on fiel.
By the time third penal arrives, you can have 5 mainline squads on field in OKW case and 4 grens+HMG/sniper in ost case.
This is why penals are strong and have to remain so to have a balanced early game.
Do not 1v1 them, because with superior squad count there is zero reason for you to do so.
You see a problem only because you ignore solution that already is present.