Jtkoupal just responded saying the effects of batting order over the long run is minimal... If the opener occurred every day, sure, Mike Trout batting 5th will result in less PAs over the season. Openers don't happen every day, so the long term strategy you're describing doesn't really apply. They can stack the batting order 4,5,6 on games there's an opener. On games when Berrios starts, Trout is back to hitting 3 or wherever he normally bats.