I'd really like to do Scientists - Technicians, academics, and researchers, from an article in Freelance Traveller 4, but I can't locate the author and ask for permission. Similarly, I'm not sure I can get permission to do Terrorists - from an article in Space Gamer 46. I will probably come back and do some of the others later, but I think they're of limited interest.
There's always a need for quick-and-dirty NPCs to assist and confound player characters, and Citizens fills the bill. I considered adding the character classes from Book 1: Characters and Combat, but since it's so easy to create characters with the applications I've already done, and they cover the same character classes as in Book 1, I've decided not to do that. But I am going to add in the bonus class Assassins - From Paranoia Press' Scouts & Assassins.