I don't know about the scopes and scanners, but different barrels on guns would, I imagine, require CCP to have to re-balance all the weapons, AND new weapons parts from scratch. And I guess the different types currently available for each weapon pretty much are the same as having a bunch of parts to swap out, albeit with much less control over the final performance. That being said, it would be pretty cool to have a system something like the second Army of Two, where you could buy a basic gun (lets say an AR for example) and swap the barrel, scope/sights, receiver, butt stock, or clip to drastically and specifically alter a weapons performance, or add wacky sh!t like a grenade launcher, or (something I would love to see in Dust) a steel shield to your barrel (i'm not a heavy, but I think it'd be scary/cool to see a heavy trundling towards you, HMG wide open, peaking through the little eye slot of his gun mounted shield while bullets ping off it. Again, all this would totally nerf current balance I think). This stuff might help with some issues that aren't balanced. Yea, you could build an AR that hits like a jackhammer up close, but to do this would require parts that destroyed its range.