I know what OP means,
In a 3d game you'd have the advantage to really look from far away and get a precise shot, often one hit kill... but compared to a regular FPS, in Soldat the maps are much smaller, with fewer places to hide and with most of the action happening in face to face encounters. There's been people saying that the bink against autos is completely null at times, and while that's true, it's not really that much of an advantage or otherwise people would use Barrett a lot more in the competitive scene and that's not the case, so any attempt to diminish Barrett's features, specially against other weapons, would make it more unusable.
I believe people use it more in public servers because it's 'fun'... and I'm not denying that being one-hit-kill is another important part but many autos combined with grenades can kill almost as fast too, not to mention that in theory the auto should be dealing enough bink to make the Barrett user miss their one shot... but yeah, using the weapon is quite fun and challenging, and that explains a bit why servers like Oneshots and SnS are so popular. (some people here have told me that they feel the game in these servers be more fast paced than the regular ctf game)
So I think the disadvantages outweigh the advantages for the Barrett and with the variables to tweak, and the limitations of the game, increasing power could be beneficial imo; It won't make the Barrett too overpowered because it's already one-hit-kill but causing additional damage would be a nice feature... maybe the walls part is a bit too much and that involves more than just changing the weapon balance and I don't think it's a good idea.