Many of the law changes aimed at making the game a tv spectacle, in the Super League era, also had the effect of encouraging bigger, impact players. This created a situation akin to NFL where size and intensified for larger collisions. Once upon a time the answer would have been to reduce interchanges to encourage fatigue but with modern prep some of the big lads are doing almost a full game.

I suspect the skull cap protects the outer skull whereas the brain getting rocked inside the skull is the concern.

In RL we tend to tackle the chest stopping the body in its tracks the issue with this type of tackle is that the head continues to motion forward then backwards like whip lash which moves the brain inside the skull. If we tackle around the waist the upper body will continue to move forward with the neck and head with no whip lash effect.

Agreed, head in the wrong position or hitting a knee during the tackle.
If we go for "nothing above the waist", we're almost playing touch and pass.

The amount of offloads will increase ten fold. What a stupid idea!

Most RU props dont have waists...