Royal Engies are in the same situation with their docrinal flamers. Personally I don't think it is a big deal.
Yes and no, because they have the cover-bonus-system [cooldown multiplier 0.83 (1/1.2) and reload multiplier 0.71 (1/1.4)] AND get massive fire-bonus at vet1 -70% cooldown in the cover +50% reload speed in cover AND vet3 -33% received accuracy. Don't forget the option to upgrade Bren and 5th men-upgrade.
[Edit: the cover-system is from 2016, I am not sure about the current bonus-system. I am sorry, I will check it now.]
So, more or less they arn't in same situation, because instead of Ostheer's Pio, Royal Engineers can stay in action way longer, with Vet3 min. 33% longer. With 5th men ~ 53% longer.
......
And here is my point.
a. make them looking more unique with Luger, so they can stay at the current DPS-balance (Luger instead of bad version of MP40)
b. boost their upgrade while give a logic indicator for the buff-situation (Luger -> MP40)