Assault Engineers, Assault Grenadiers, Assault Guards, Paratroopers, Cavalry Riflemen, Rangers, and Urban Assault Light Infantry
You know what is a common for all these units and not for ppsh cons?
They load their guns with real bullets instead of "bang" flags.
Con ppsh is LEAST effective CQC weapon in game, its less effective then certain rifles and assault rifles that deal great damage at mid and long range as well.
Alternative to giving con ppsh survivability buff post upgrade, you can always buff the dps of ppsh themselves, so they actually kill stuff once they are on top of it, because with current DPS, they certainly don't.