I'd be in favor of removing the mentor class entirely, and replacing with the ability for anyone, after a certain account age, to become a mentor without losing a class choice. I tried the mentor class for sometime, but found it to be dreadfully boring. Not at all worth giving up another class. If any character could do it without penalty then one would likely see more active mentors.
Allow a small prestige bonus for new nobles who choose a mentor, and additional small bonuses(prestige or skill increases) for those who receive good marks from their mentors. For the mentor, all the current ability to write a book after a certain number of students.
