I keep hearing this argument and it's one of my pet peeves. The dual-to-single Schreck change was so far back in the meta it's not even funny, any considerations are COMPLETELY invalid. Just to mention a few things, Panzergrens had armour then, small arms were much less effective vs infantry, veterancy gave huge survivability bonuses for Axis squads etc. This is a completely different game now.
Panzergrenadiers are expensive enough and squishy enough that giving them one Schreck would not break the game.
And guess what, especially in team games, Axis still blobs. Two PzG squads with one Schreck each or one PzG squad with two schrecks and one unupgraded - what's the difference?
Naturally a single Schreck should cost 80 ammo.
Regarding the Volks blob, Schrecks are a much better option on Volks because they are a low DPS, 5-man squad with good veterancy bonuses. Schreck is perfect on them - it gives them XP, gives them a role, they can absorb a lot of firepower while still retaining their AT, and losing a single Karabiner is a negligible drop in DPS.
Whether this mod should address PzGrens is another matter. I do not see PzGrens as breaking the meta in any way at this moment.
Maybe decreasing range on Schrecks so that blobs may actually be hard countered by T70 or AA halftrack