Just so you know, the M416 was already in Battlefield 6 at launch! It's known as the DRS-IAR. It's based on the USMC M27 IAR, which is an HK416, which is what battlefield's name "M416" comes from.
The DRS-IAR is considered a "LMG" in Battlefield 6, which is actually a really amazing nod to the rifle's real life procurement story in the USMC. The Marines wanted something other than the M16, so the USMC found a way to request a replacement for the M249 (an LMG) and the result was the Marines adopting the M27 (remember the M27 is an HK416) as a hybrid "Light Machine Gun" / "Assault Rifle" which is exactly the way the gun works in Battlefield 6. The DRS-IAR is in the LMG category, but it really plays more like an assault rifle. Just like the marines.
It's unfortunate that Battlefield 6 didn't use the real M27 name. But there's actually a wonderful hint toward this as well. In the early versions of the game, including the beta, the weapon inspect animation would show the "M27" white letters on the magazine well of the rifle. While the weapon model was eventually patched to say "DRS-IAR" instead, if you tilt the weapon inspect at just the right angle in the firing range, you will see the light bounce off a dimpled "M27" right where the DRS letters are. So the developer found a way to hide it there anyway!!
tl;dr - the DRS-IAR is 100% an authentic M416, and you can build it out just like the M416 in previous battlefield games.
P.S. If you want to play with the M416's larger caliber sibling, the M417 is also in Battlefield 6, which is known as the real life HK417 which is just scaled-up version of the HK416.
