Here's something - I don't think just anyone can teach (anything really) especially Martial Arts. There's a certain art to teaching that's different than the science of teaching.....I'm not really sure if I know how to express it in words.
Think about when you were clawing your way through the first five years you were a student in a dojo. There was probably more than one person that taught classes. I think we all had our favorites, kind of human nature. I don't think that "favorite" had anything to do with class being easy or hard, or what the rank of the teacher was, it was more how the teaching applied to you, personally. Maybe it was a motivation the person inspired in you, maybe it was the way he/she spoke/explained, maybe it was something else.
I think, when there's different teachers in a dojo, some teach some things more effectively than others. Some might be better at technical aspects of position, some at fighting, some at kata, some at stance and footwork, some might know how to express what adaptability is.
Any thoughts on this? Do you think that anyone can teach?