Symbolic roadway communication

On the way home last Sunday, I must have counted 3 cars with only one working headlight.  I always want to be a good Samaritan and let them know (especially since I apparently was one of those cars on Thursday), but I never know how.  I can't get behind them and bright them, because then I'm some jerk who desperately wants to pass.  I can't get in front of them and flash my brakes a few times, because that could either mean I was a drunken fool or any number of alert sorts of stuff (e.g. "Your left tail light is out," "Your trunk lid isn't shut," "Your truck balls have fallen off and are in that ditch back there").  So my question is, how can we reach other drivers to tell them important information while being polite and specific?

The obvious answer is symbolic roadway communication.  I'm inventing this right now.

We have some vocabulary in our toolbox already.  For instance, honking.  The problem with honking is that it could mean "get out of my way or I will accidentally (perhaps purposefully in some cases) kill you," "stop driving erratically, I am frightened," "I saw a cop back there, watch out," or "my car is really old and honks when there's a bump in the road."  We also have braking, which on any roadway can communicate very different things depending on its duration/frequency.  Frequent flashes of braking by the guy in front of me on the highway tell me that he is an idiot who is tailgating someone too closely.  Rare braking of less than a second or so tells me I need to let off the gas for a bit so I don't rear-end the guy in front of me, braking of a little more than a second tells me I need to apply brakes myself, and everyone braking twenty cars up tells me there will be a traffic jam.  Also, we have brighting, which to my father means telling the SUV in the oncoming lane that he shouldn't have two headlights and two fog lights, and to some people at a four-way stop it means "go already you moron, you're at the righthand side of me, therefore you go first, can't anyone in this state navigate a four-way stop?!"  (The answer is no, in most states I've experienced.  I just start pointing at people.  You got here first, you go.  You got here second, you go.  Now I'm, NOW I'M GOING DON'T CRASH INTO ME thank you.)

But my point is that none of this means "Check that left headlight of yours."

So wouldn't it be nice if we could agree that sitting behind someone and flashing your left blinker three times means "your left tail light is out," and getting in front of someone and flashing your right blinker three times means "your right headlight is out," and getting in front of someone and braking a few times in quick succession means "you really ought to get out of the left lane"?  Sure.  But what do we do if the center brake light is out?

I know today's drivers have a lot to learn already in terms of yield signs and stop signs and stoplights and speed limits and traffic circles (don't get me started about traffic circles), but I feel like if the NCDOT really put their mind to it they could teach people this "language" or something similar and then people who have nonworking lights could fix the problem before they got ticketed, or worse, crashed into.

And quickly, I realize that this is unrealistic if not unreasonable and that it might pose even more danger given that in addition to paying attention to distances and speeds and car maneuvering, people would also be telling each other things.  But it's something fun to think about.