so in the first part of your post you tell me they used it to lay down heavy amounts of fully automatic fire on enemy positions and then you tell me they didn't use it as LMG. i wonder what the "traditional LMG" role was again?
and if you use a gun for "heavy amounts of fully automatic fire on enemy positions", i wonder how a gun that doesn't have changeable barrel and has a whopping 20 round capacity can be effective in that role.
as for the bipod, from what i've read, it was heavy and cumbersome to use, which i assume is the reason why the soldiers just removed it to save the weight. so basically it was another poor feature of the gun.
the problem is that regardless how you look at the BAR, the way it performs in the game compared to other weapons is imbalanced.
i'm sure there wouldn't be a problem if you could shoulder the BAR, dump your 20 rounds mag in direction of enemy, go back in cover to reload and regain some strength to shoulder it again and repeat. the issue is that there isn't ever any reason to do this, because your soldier doesn't care how heavy the BAR is and can shoot while standing just as well as a springfield or garand. except with 20 rounds magazine and full auto capability.
the other side of the problem is that if you say that the weight of BAR isn't enough to not only prevent it from being shouldered, but also fired accurately while shouldered, why the hell can't you do the same thing with type 99/96? are you telling me that a gun that weights 8-9kgs, or double the average rifle can be handled just as easily as said rifle, but if you add 1-2 additional kilograms, it's suddenly too much to shoulder it at all?
again, what in reality was too heavy for rifle and too flawed for LMG, in the game is for some reason best of the both worlds. and keep in mind USA already has a significant edge in firepower even without it.
If I fired my entire 50-round Thompson magazine at a Japanese bunker to suppress the troops inside, am I not laying down automatic fire on an enemy position? This is not something which is exclusive to a "traditional LMG" whatsoever. In my mind, a "traditional LMG" is a fully automatic weapon which fires rifle caliber rounds from a prone or rested position using a bipod or a tripod. I also believe a "traditional LMG" would not be able to be fired from the shoulder for significant periods of time.
I agree that the BAR is a little bit too easy to use in-game, but I do not agree that the BAR is the useless subpar weapon you portray at is. The BAR in real life was a very powerful (was most often issued with .30-06 Armor Piercing ammo instead of the standard .30-06 Ball) and accurate automatic weapon which accounted for many Japanese casualties in the Pacific theater of operations. Many US Marines found it to be at its best when used as more of a shoulder fired rifle with a fully automatic fire mode while the M1919A6 filled the role of support LMG.
The best way to make the BAR less unbalanced in the game imo would be to make it go into iron sights slower than it does currently which would help simulate the fact that it is heavier than a Garand or Springfield.
The reason why the Japanese LMGs can't be shouldered is very simple: they were not designed or meant to be shouldered. They do not have the proper sights, forward grip, stock, or magazine placement to be effectively fired from the shoulder like the BAR.