Don't mess with NFHS encroachment. It is so easy to administer. The first one in loses. You don't have to keep up with "Was he head up or in the next position over?", the center doesn't have to make a decison to snap it and hope the official sees the same thing, etc. Reduces sideline arguments immensely.
I agree with adding uncatchable to high school DPI.
I'd like to see the "four on one side of the ball" added to the free kick rule. As more and more are using the on-side kick, it would reduce injuries.
Eliminate the toss and choice in OT. Visitor team get's the ball first, home team second, and we play at the end where the offense can see the scoreboard (no advantage to that, but it just makes it simple).
Adopt NCAA intentional grounding rule - just treat it like a sack. A keeps the ball (except on 4th down) at the spot of the pass, loses down, clock is wound on the ready.