Hi
I like the girls You described, i think it's great that You made them "deserving" for a spanking. And that's why i think that the smart, bookish girl should be a little modified, maybe it could be told that she is arrogant and thinks she is the smartest and other are dumb? Or she could be some computer hacker? Of course it's just my ideas, i know that You may not care about them being "deserving". But if You care a little then maybe something of it You will like

Ah, and the rich girl, is easy to think, that she can be haughty, arrogant and spoiled, so - for me - she is deserving already
Okay, here are some my ideas for the characters (names of course can be changed

), maybe You will like some:
Daphne - Sly, sneaky, inteligent girl that poses as good and sweet. She is secretly naughty and makes all kind of trouble but she blames it all on the other girls.
Brittany - Good natured but rather dumb, easy controled and put to trouble by the smarter girls. Also clumsy, always doing something not right or breaking things.
Miki - very immature and with childish behaviour. Very spoiled by her parents and things that she can do anything. She likes to do stupid pranks, can be mean or even rude (without understanding what she is doing, like a little girl).
From my other ideas there also one that the spanking depends on how much someone loses. If the lost is complete (for example the one who gets the least points) the spanking could be the worst (but it doesn't need to mean severity - it could be a picture of a spanking in front of all the other girls for example or/and a need to stay bare bottomed also in the next round).