I think there is no change needed. of course it is different but you have also to consider that in cs 1.6 smoke can make a whole corridor "sniper-safe" (at least from one direction). In cs2d a smoke grenade hides only everything in its closer range because of the top down perspective. everything else is still visible.
If I would make the smoke more transparent I could also remove the smoke grenade from the game because it would be too weak. And adding something that makes your whole screen smoky when you stand close to a smoke grenade would be a pretty stupid effect in my eyes.
no way that I change something there.