Again, you're expecting too much from SW IT. I don't believe their systems would accept that without major code changes. Cheaper and easier on them to do it all at once.
I've already seen reports, I don't recall if they were here or another message board dealing with Florida travel, of those that had changes to their itinerary that had their tickets changed to basic with the baggage fees and credit expiration when they changed from what SW rebooked them on. I stand by my belief I posted a month ago. If you accept the WN auto rebooking, your booking will remain intact as initially booked, any user initiated changed, regardless of the reason, will change the ticket to basic with it's restrictions.