Eh, I considered both of those too, but the SMAW and the NLAW are both also one-shot weapons, which is why I had Scott chose the Carl Gustav. Not much point being the 'anti armour specialist' if you've only got one shot to do it with. 
Also the 'Charlie G' never comes up in anything, and considering the SAS used one to put a hole in the side of a warship in the Falklands, I imagine there's a pretty healthy respect for it among Scott's colleagues. And I wanted to use one as well.