Might as well change the name on the back of every jersey to "Nancy" and make the players wear flags.
That's right, tell them ligaments to toughen up!
It's a violent sport played by giants where the action happens way quicker than I think some here realize. It's as if some think defenders always have the time to stop and think where they are going to hit the other player. Now we're supposed to allow only 1/3 of the body to be touched while tackling? Ok, tell me how that works out when a smaller CB is meeting a guy like Gronk or Ladarius Green head on in the open field. It plausible these smaller defenders will start getting injured more, or offenses become even more productive than they already are.
Defenses are basically hamstrung as it is, and now you're advocating making it worse.
Injuries are going to happen as long as there is contact. Look at the unintended consequences that have resulted from the recent rule changes. Guys are getting taken out left and right, I don't recall every seeing so many injury TO's before this year. You restrict the area that can be hit even more and I'm sure there will be another hole pop open in the dam.
I'm tired of seeing offenses get another set of downs because their QB received a love tap on the head. I'm equally tired of seeing legs bent backwards because the league overreacted big time. At some point the league needs to just realize this is going to happen and maybe provide more incentive for better tackling techniques.
These guys choose to play the game, they know the risks. Of course there is a place for rules to protect player safety and long-term health, but what's being advocated is going too far.
Like Donohus said, let technology solve this problem.