In regards to extending the play clock from 25 to 40 seconds, I am fine with it. The extra time might improve execution on both sides of the ball. In addition, a longer play clock should reduce the number of actual plays during the game which might reduce injuries. I also believe that this extra time gives the teams some extra strategy.
In regards to instant replay, I'm on board with it for championship games or if a venue already has the equipment to properly facilitate instant replay. I am personally not a big fan of instant replay (disrupts the flow of the game, adds additional time for the game). I do however understand that some blown calls have an even bigger detrimental effect on the game.
On a somewhat related note, we should look at improving the quality of officiating for all sports. There's a shortage of referees and many of those who ref for a year or two end up quitting because the compensation is not worth the abuse. I'd be fine if there was some sort of system that measures the fan interactions during these sporting events. If the fans are excessively abusive to the coaches, the players, or the refs, they should be held accountable. Obviously the NCHSAA can't fine the spectators, but they can hold the hosting site somewhat accountable for enforcing good sportsmanship. Any fines levied against a hosting school could be placed in a general pool of funds that would be doled out to the refs after the completion of the season. I imagine some schools would rather ban certain abusive spectators from the game to offset these fines. In addition, removing some of these abusive spectators might encourage others to actually show up for sporting events.