The U should always wait for the ball to actually be ready for play just like the R does with a 25-second play clock. This includes the other officials being in position including the chain crew (back chain or box is sufficient). The 40-second clock doesn't suddenly make us have to hurry to get the ball down and back out of there immediately. We still control the pace of the game. The ball will often be down in the 28-32 range and the umpire will usually step back within 2-3 seconds (12-15 second pace target for the previous play clock rule). But if the ball is down at 36-37 seconds (i.e. runner down at his feet and hands him the ball immediately) he may want to stay there a couple seconds longer to make sure the crew is ready for the next play.
Very rarely will the offense be ready to snap immediately when the U steps away. In 3 years of doing this in HS and 6 or 7 in NCAA I've never had to ask a team to wait for me to get into position. It's not a bad thing to ask, but it will not likely be an issue. Your coaches will think this will allow them to snap the ball with 30-35 seconds left on the play clock every play, but they'll realize they can't go that fast regardless of what we do. I saw it happen in NCAA and I saw it happen when we started our HS experiment. Reality is no team goes that fast.
The beauty of this is regardless of whether the ball is ready at 32 seconds or 23 seconds the offense still has 40 seconds from time the ball is dead to when they have to snap it. It's not about how fast they can snap it on the front end.
