Technically, Jeff, the course is still certified. The methodology does not require a calibrated bike, or a steel tape.
They would measure (Jones Counter) from a common point on both courses, to the old Start. Record counts. Ride the course back to the common point, then compare counts. If within tolerance, use the one that gave the longest measurement. That is how far you will now ride to the new Start location. Make a mark, then ride back to the common point. Compare counts, and adjust as necessary.
Thus, you have taken the same distance that the old Start was from the common point, and relocated it to the new Start, the same distance from the common point.
While this allows the course to remain certified, one has to ask "At what length do we require a complete re-measure?". In my opinion, this is reaching that point. My initial response would be "no more than 25% of the course length", but this is only a mile. If we had the 25% threshold, that would be 10k for a Marathon. In that case, a mile is not a significant amount. Open for discussion.
I would suggest to the race director, that while the course is still certified, they should consider a complete re-do, as it gives them a 10-year life. Of course, they may also be thinking that if the new configuration doesn't work out, they will change it again, and don't want to spend the money until they are sure the course works.
Anyone else have a threshold for course modifications before a complete re-do is required?