The reason that Osttroopen/Assgrens are meta is because Grens are the only mainline infantry that cannot be build from the headquarter. On multiple maps this allows the allies to cap vital points/buildings. This forces you to attack with the defencive oriented grens. Instead of buffing the grens you should consider making them buildable from the HQ again (and the MG back to T1).
Also, the 5 man Grens are crutch that needs to go. It overshadows the other commanders (on maps where you don’t need to rush buildings)
That's an interesting idea but I think Grens would need to be reworked a bit for that to work. Here's my suggestion:
Grenadiers swap places with HMG42
Squad size increased from 4 to 5
Gren Kar98k damage reduced from 16 to 14
Squad cost increased from 240 to 280
Vet1 medkits now Free
Veteran Squad leader upgrade replaced with normal G43 upgrade
this would help LMG42 and G43 upgrade make a come back, and reduce the need for Osttruppenn and Assgren.