I don't think there is any doubt that Mesoraco will start in Dayton unless he really struggles in spring training. Despite what you think you can see in his numbers, the Reds saw him in person and know whats up with the kid. He won't start in Billings.
As for Stubbs, even if he has a bad season (sub .800 OPS) its not exactly bust city, but it gets a lot closer. However there is nothing that suggests he is on that path. I see him splitting time between Sarasota and Chattanooga next year, hitting much better in Chattanooga than Sarasota.