If Southwest allowed their tickets to be sold on other platforms, these "no scheduled service" problems would disappear because the computer would piece together an itinerary just like they do for any airline. I've seen domestic AA itineraries that involve overnight 9 hour layovers in places like LAX because one wants to leave in the evening and a red-eye is not available, or there's a sale to and from LAX. The total fare is really two fares because it's >4 hours, but the user doesn't care about that, only the total price.
Southwest has a lot of positive qualities to it, but their insistence on sticking to the old way of not selling tickets on any platforms other than their own makes no sense.
If you fly to 12 airports with two schedules (Saturday and Sunday-Friday), it doesn't take too long to manually build itineraries for all 12*11*2 = 264 possibilities. But when you fly to over 100 destinations and the schedules vary by the day of the week, the number of possible itineraries is many thousands.