STG-44 it's too big for volksgrenadiers.
Wrong, StG-44's were in widespread use by Volksgrenadier Divisions in 1944 and 1945. Once again, the defining feature of a Volksgrenadier Division was the widespread use of automatic weaponry. Volksgrenadier Divisions were undermanned and undertrained, and the widespread use of automatic weapons was meant to offset this.
Here are Volksgrenadiers in the Ardennes using Sturmgewehrs: