Hi 1984poke. In my opinion...you are overthinking and worried about nothing. It doesn't take a "few days to get back into the groove". Plus, you can hope all you want, but unless you cancel your current order and place it again later, it will be built when it is built.
And yes, I know about the old "You don't want a car built on a Monday or Friday" types sayings/advice. But that is an old saying.
Concerning your build weeks questions. The week of 12/17 begins on a Monday and runs through Saturday, 12/22 (or whatever day the Christmas holiday begins). So we are actually only discussing a shutdown of approximately 3 weeks. Plus, as ice-capades has discussed, there have been problems with the ordering system, so we may have incomplete information.
I understand your anticipation and anxiety, but you'll be much happier if you can relax and stop worrying so much.
I hope your shiny new MKZ comes as quickly as possible. Good luck. ?