As for a director SMing a show, I think that it would be a bad idea. I've never had to experience it, but because of the multiple tasks required by both directors and stage managers, I just don't think it would work. However, in the high school format I work with, I've found that assistant directors stage managing works well. We've done it a lot, as our AD's are usually students, and don't need to do much else during tech rehersals that the director can't.
Now, just imagine a director/LD combo, or director/TD combo...
