In the iron-sighted SMG versus LMG discussion, I'd argue that since a LMG user is going to be unloading on full auto, the suppression would quite possibly throw the submachine gunner's aim completely off.
But there is no way the old RO1 method of right clicking to raise the weapon should be brought back, that was simply terribly unrealistic and unnecessarily clunky. That's simply not how LMGs are used for hipfiring, they are not that terrible nor heavy that keeping the weapon aimed foward by the hip is so tiring, or such a hindrance on movement, It just wasn't. So don't even think about it.
That's simply not how LMGs are used for hipfiring? What, you don't need to physically lift up a light machine gun to hipfire it?
Do me a favor. Get up, find a heavy textbook, preferably a math or science one, and hold it up in your left hand in front of you. Keep your arm fully extended. Pretend it's the bipod of an MG-34, and try and swing it left and right several times. Let me know how long you can keep that up for.
There is just no basis for an argument on realism grounds that the LMG was always held in a hipfire-ready position. It's an unnatural position, it DOES take effort to maintain for more than a minute, and you sure as hell aren't going to be walking around all day with the weapon held like that.
Now, go out to the gym, pick up a 25-pound dumbbell, and try and jog around with it in your right hand while holding up the textbook or a five-pound weight in your left. Keep your right arm bent, because if you straighten it, the barrel would be pointed at an upwards angle. Let me know how that feels.
And no, the sling won't help with this, because it's too short--you have to push the weapon forward from the sling's natural resting position and flip the weapon upright (sling loops are on the botton of the weapon), meaning that the length of the sling fixed to the barrel is carrying virtually none of the barrel's weight. In fact, in the two examples I've seen of hipfiring actually being used in 'combat', the sling isn't even being used:
At 0:44:
The Wehrmacht - Combat Footage - YouTube
and
MG-34 Hip Shooting - YouTube
Just LOOK at these videos. They're not jogging anywhere with the weapon held like that. The guy in the second video is also coming dangerously close to blowing his buddy's head clean off.
Finally, I can guarantee that hipfiring an MG-34 was a method of last resort in Stalingrad fighting. Why? Because the Wehrmacht had ceased using the 50-round drum for the MG-34 in the infantry role by 1942. Instead of the 50-round drum, machine gunners carried mainly the loose 50-round belt. Given the MG-34's finicky propensity for failing to feed at times, there's no way you'd trust that the belt of ammunition hanging from the weapon or draped haphazardly across your left arm would feed properly in hipfire with an enemy just meters away.
Never mind the fact that your NCO would chew you out IRL for trying to participate in room-clearing with your valuable weapon. Never mind the voluminous infantry doctrine stating that the MG34 is to be positioned and used to cover open ground, and that the entire infantry squad must support and protect the machine gun. Never mind the fact that IRL you'd be traveling with two ammo handlers and an MG team leader, who would be leading the way with his MP40.
The fact remains that holding the MG34 in hipfire mode is impractical, cumbersome, and tiring, and only used as a last resort or when enemy resistance was so pitiful that friendly troops could literally stand in the open to return fire.
Iron-sights-to-hipfire is the way to go. It's realistic, and it reflects the fact that no sane machine gunner would carry their LMG ready-to-go at all times.