Restrictions on where and how the QB can be hit, more protective rules on hitting defenseless players, penalties for scoring celebration, etc. Personally I think overruling on the instant replay qualifies.
There is an old pic of Y.A. Tittle that makes my point. Google: y a tittle bloody photo
That has nothing to do with attracting female viewers. It has to do with protecting quarterbacks, because a star quarterback is a money maker for any team.
Most of the other rules have to do with future lawsuits more than anything else. A sizeable portion of ex-NFLers are now either crippled or have scrambled brains. The league is trying to protect itself from future legal action.
Has zero to do with attracting female viewers.