LMG Grens always have a hard time killing retreating or flanking units. The LMG always have to stay still/laydown whenever they are going to fire and have to rotate in order to fire at their target and the LMG gunner has the rotate speed of a tank. Maybe give it as a bonus to veteran LMG grens to fire on the move? LMG42 is best used defensively yes, but VSL upgrade on Germany infantry commander is much better compared to the Bolster squads from tommies. If VSL was nondoc LMG would be rarely used since VSL gives much more survivability and some dps making them able to punish retreating squads.
I suggest to make LMG upgrade cost higher so that they can fire on the move or give it as a veterancy bonus.
Or.... use G43s, which do exactly what you want and for less.