The rules they have to change are; (1) the helmet-to-helmet rule, which can get called when there is completely accidental contact that occurs because 2 (or more) players are moving very very fast in a small space; and (2) the helpless receiver rule, which makes it virtually impossible to tackle a receiver in the open field since the defender has to make a sure tackle AND not make that tackle too violent.
I'm all for protecting players, especially their vulnerable brains, but the helmet-to-helmet rule can't be a zero-tolerance rule (the refs have to have more discretion NOT to call the penalty when completely accidental) and the helpless receiver rule -- well, I don't know what to do with that, since it's called so inconsistently.