Right. Minerva misusing her position would be a real challenge. I generally see her as uber-principled, so that would be tough. But I would trust you as a writer to make it believable. You've spent enough time examining her character to know the chinks in her armour, so to speak. (Come to think of it, I recall reading a McG/Sirius fic, ages ago, that might have been a bit of abusing the student/teacher relationship, but I can't think where I might have read that.)

Not that I'd, you know, say no to more of your femmeslash or more of your McG in general. Just sayin'. ;)