[donofriose]

Make an attempt at wrapping up mandatory so players will actually have to learn how to tackle instead of just throwing their shoulder. I realistically believe that is the only thing you can do. It forces defenders to use form which prevents concussion and is extremely easy to spot when a player does not wrap vs. when they do. If a player just does not wrap and just throws their body/shoulder automatic penalty. Rugby has this rule and that is why concussions are not as frequent in professional rugby as they are in the NFL.
If you do not want to do that leave the rules alone. Too much gray area. Have an absolute line or no line at all. You cannot make small changes every year to hitting, it confuses the players, confuses the fans, even confuses the refs at times. Plus we all know its just so the NFL looks like it cares. Make it easy, or don't have any rules in regards to hitting.