Mustoe's not ready yet. And he also represents pretty much all of our depth at OT, so he needs to get as many practice reps as possible at tackle (game reps too) so that he would be ready if we had an injury.
As the depth chart stands, Mustoe also has to be developed to be our starter at LT next season.
On Sunday, the coaches actually got him in as a blocking TE in a couple situations. That at least has similar footwork as OT since it's at the end of the line. Anyway, it's not a bad idea. But I think that as it currently stands, Kelley is better at guard than Mustoe is at guard and Handler is better at center than Kelley is at guard.
Honestly, I'd be happy if an OL of Harris-Crabb-Handler-Munyer-Nembot held up all year and the coaches could systematically develop Mustoe, Kelley and Cotner as quality backups while redshirting all of the freshmen.