are you trying to invalidate the usefulness of the tommies' squad size?
and the grenadier should not get a fifth men. The wehr is the glass cannon faction. Their infantry get the easiest access to firepower in exchange for speed and durability.
This is also why giving the uber mortar and dual lmg to the USF utterly breaks the balance. The USF shouldn't get the uber mortar and the wehr shouldn't get a fifth man on their grenadier.
The most the grenadier should get is formation adjustment and Received accuracy buff.
Tommies don't get more expensive to buy once you get the 5th guy, and they can pack 2 LMG's per squad. If every gren squad was 5 men, and cost more, then you'd be paying more manpower and popcap per LMG you wanted on the ground.
Brits don't really need to consider this because they need those tommies anyhow for medics and FO teams. You buy grens because you want an LMG squad (and a snare). You buy tommies because tommies are the core of the faction, and then you put LMG's on them because everything is better with LMG mayonnaise.