That's the problem, though. A soldier in RO2 can expect to be within 100 meters of the enemy very nearly 100% of the time. It makes no sense to use march-carry as the default state because there is no scenario in the game where anyone would ever do that, not to mention that you don't really care if your character is comfortable, anyway.
This touches on the root problem with the MGs not being as dominant as they really were, too. You take a weapon with an effective range of a kilometer and stick it in an environment where you can barely even see a person standing in an open field at 250 meters and it's guaranteed to not be as useful.
Just because you know the enemy is near doesn't always mean you think you're in imminent danger. I don't think it's appropriate to decide that, because we are assuming that the player is always in danger, they shouldn't have to make their own decision about how to carry the weapon. It's like the scope/iron sights view on the sniper rifle. If they decide that they're going to use a precision weapon intended to excel at 200 yards or more in a knife fight, they're going to have to change views beforehand. Except that in the case of LMGs, this decision will be waay more convenient to make, since you don't have to reach all the way for that "6"key...
On a map like Apartments, sure, a machine gunner would probably be more incentivized to hold the weapon at their hip a larger proportion of the time... but firstly, the maps are changing. Coldsteel, Univermag, Rakowice, Gumrak Station, Bridges of Druzhina, Winterwald, Barashka, Mamayev Kurgan...
Why would you not want to hold the thing in out in front of you all the time? Well, if you're taking advantage of the strap, then it's low enough to interfere with your hip and leg movement. If you're cradling it in your arms, then you're holding the whole weight of the weapon. The length of the weapon and the arms of the bipod make it difficult to squeeze through that hole in the wall. And if a 250-round belt is hanging out of the left side of the thing, then you've got a whole new set of problems. It's cumbersome and really only worth it if your life is in imminent danger and you can't rely on allies for support.
I mean, what will this change really do? Please disregard Apartments. In terms of level design, its one of the worst possible maps to try and play machine-gunner by actually deploying the weapon.
To the general audience, look on the bright side. If these changes are implemented, it just means it takes more skill to use a machine gun in close quarters than it does now. It adds challenge to the game! Now, when you see a machine gunner really laying it down in close quarters, taking up a stance atop a stairwell, blasting two hostiles into pieces, sprinting to a hallway, lifting the weapon and spraying down three more enemies, you respect their mastery of the game mechanics. It's something you learn to use and get good at, like anything else. It's like good Starcraft micro. I don't see why that's a bad thing.
EDIT: After seeing the below post... for the last time, it's not OP. It's just unrealistic.
And for the benefit of those who never played RO1, this is what we're talking about. See 3:40. It takes one second to deploy for hipfire. Is it really THAT bad?
Red Orchestra German Weapons - YouTube