That is a good idea, but we usually use Charlie or Delta on our flights. We have had a complete change of flight number before, which is always a good clue to a change of route.
I think I might suggest to our Ops Dept that they change part of the flight number so we know it is a re-route as I feel it is only a matter of time before we have to tech stop due to a longer re-route being discovered once airborne.