I'm going to hazard a guess that the most likely scenario is not that we go 15-1, with Romo suffering a career-ender before game 16. More likely is the Romo out = team tanking-type season, meaning Garrett too is gone.
So then the new coach becomes the likely determining factor. If it's a puppet, then I think Jones would most likely go the young washout route, and Locker would be a horrifically likely choice. Maybe even Pryor if he shakes loose from Seattle. Again, coming off a likely bad season, Jones will feel the pressure to sell some sizzle, and if he can do it on the cheap, so much the better.
If it's a real coach, you have to factor in their ego/comfort issues, like with Holmgren/Weeden mentioned above, or Parcells/Testaverde/Bledsoe. Fortunately, Rex Ryan won't be looking to bring Sanchez, but I'm not sure you trust his QB evaluation skills, either.