Judo., I love submissions but at least in my experience BJJ doesn't work enough takedowns, b/c its so easy to just pull guard...Munky can give you more info, but I know that legit Judo schools work alot of submissions as well as the throws. The reality is you are not going to slap an armbar on somebody in a bar, but the throws and body control you will learn will be very beneficial in the typical bar fight or need for self defense...Grappling alone isn't the answer though. Tell your friend to find a boxing or muay thai gym and get at least a basic skill level in striking.