100% agree with this WLW, it'd take a few weeks for players to get the message, but if refs stuck to their principles and booked anyone other than the captain who argued with them, players and managers would soon learn. I'm also a supporter of goal-line technology and, further in the future when perhaps a system has been developed that is efficient, reliable and quick, some form of a challenge system (one per half per team as Amit recently proposed for example). I think teams would then employ tactics whereby we'd mainly see these challenges reserved for 'in the box' decisions only, which is where lengthy stoppages occur anyway while referees sort out the ensuing bedlam and thus it wouldn't really hold the game up much more than we see currently. Still, the first step would be to implement the Captain-only rule when speaking to the ref.
This actually isn't as far-fetched as it sounds; think of the number of officials in tennis watching each line on the court for instance, who are there to aid the Umpire's decision-making.