As an example, maybe an MP5A3 could be swapped for an MP5SD. If there aren’t any variants, then maybe an entirely different weapon could be used if it’s functionality is similar. If BF1 has a Gewehr 98, then maybe you could replace it with a Gewehr 88, or other bolt-action rifles that aren’t in the game.
This would serve a similar purpose as skins in League of Legends or Rocket League. The functionality remains the same, but a different feel in given to the character.
Why DLC? Personally, I wouldn’t want to see an idea like this distract from developing the game. Creating weapon models, creating the animations/other assets, and making them be represented as cosmetic features in-game would take time. It may also serve as a means to subsidize the cost of developing free content, similarly to BF4’s free maps.
This would allow more weapons to be added in without complicating the weapon balance.
Except, that is not what they meant.
They were saying that guns will have variant attachment pre-sets.
This is to help people who get confused by which weapon attachments to use.
Eg: One to increase accuracy but with a mobility penalty, or one to increase mobility but with less damage.