The MP40 would also work, may even be better, due to the fact that my suggested profile fits the MP40 better.
I don't think that the STG44 would be a good choice. It would probably be too good if it has a similar profile to volk STG and the squad would become too similar to volks(5 man K98s and STG44s). I think that these squads should feel different.
Though, I don't think this change is necessary, and the balance team should probably focus on other stuff.
In terms of making it feel different, I think the StG fits the role the best to differentiate VSL Grens from other WM units.
Currently WM can get MP40 equipped Grenadiers as Assault Grenadiers, G43 equipped Grenadiers with the G43 upgrade, MG42s as the standard upgrade and another type of G43 upgrade as the current VSL upgrade.
An StG44 upgrade to Grens would be different, as the only unit that currently gets StG44s in WM are PanzerGrenadiers.
OKW overuses StG44s in their faction design, just like WM overuses MP40s and underuses Kar98ks.
I’d like to see Relic look at real tables of organization and equipment when they make CoH 3. At least as a baseline for core units.
I mean just look at production numbers. 400,000 StGs of all types vs 1,100,000 MP40s vs 14,000,000 Kar98ks! For every StG in the game there should be roughly 2 MP40s and 35 Kar98ks!