1. The reason for the reduced number of girls

2. The new role for Mrs Garrett

3. The reason for the addition of Jo

4. Why Gary Coleman appeared in season 2

5. Why the Headmaster was removed from the show

I think the guy who was supposed to be Mrs. Garrett's companion was Howard the Chef.

"creatively unwieldy" = Both the early Hartnell and the early Davison eras of 1963-89 Dr. Who also suffer from too many regulars.