Block in the back should not be a penalty. Don't put yourself into a position to be blocked. Period. If you get blocked, you get blocked. Outman someone.
When the offensive team is in a position where a penalty would be "half the distance to the goal" (see: pinned deep) all defensive penalties should be worth half the yardage they would normally be. If the offense only get 2 yards for a false start because they're on the 4, the defense should only get 2 yards for an offside.
No fair catch. It would make the position of punter MUCH more important on the team. No, this won't lead to people dying, it would lead to more guys letting the ball go because they don't want to die, and therefore teams pinned deep.
Not a rule, but it's ABSURD that we have to watch to 70 year old men walk onto the field to measure a close first down call. We're relying solely on the first guy putting his marker down in the middle of the field exactly where it was on the sideline. Put a chip in the football, use some lasers, and knock it off.