Wouldn't that make penals the only squad in game which pays more then the actual reinforce formula indicates? You could argue merge, but that requires already another squad and they'd become even more squishy because of low defensive vet bonuses.
https://docs.google.com/spreadsheets/d/1_620_OrdXoZaFPALinbH9Nm3itFonOHvI0yNI6psLck/edit?usp=sharing
note that the svt-40 are straight up superior to the volks k98k. While I don't think that's an issue itself, it still means that the penal should really be more expensive individually.
Access to faust doesn't really make up for the difference in dps, and both penal and volks get access to weapon upgrade. I would also rather give some versatility to the penal in exchange for a price increase to ~320 mp per squad and ~27 per man.
Have the satchel charge deal heavy engine damage at 50% hp. This still leave the penal build vulnerable to light tank rush, but give them additional use at late game.