If you look at the IMAC contest calender the TAS has everything to do with it. We start contests in January and have a full calendar until July 31. After that we have almost nothing. Why? Because that's when the TAS points close. So the schedule for IMAC is driven by the TAS like it or not.
Considering that this years sequences came out in October of last year it will be over a year flying the same sequences by the time the regionals are held if in Nov/Dec. Also with new sequences out in October of this year I would rather fly some tasty new sequences and move on from the same old same old.
Another factor is the younger members as well as families - we should be able to run a season calander that doesn't use up a whole year and then some. By the end of the summer the youngsters need to get back to school, dad has burned up his vacation time and then the holidays are upon us. I think we should end on a high note with the regionals held before the TAS so they are fun and accessible to all who would like to participate. Labor Day, the last big holiday of summer, seems appropriate to me as a target for regionals.