So would you want all classes added, but only simple class definitions? What if your css class was nested? What if it was applied to a specific tag? What would you want to show as the name of the class in the list?
You could have classes like:
.main .inner .content {
}
or
h1.highlight {
{
or
.errorText {
}
or
#bodyText .leftside {
}
some classes could only be used for positioning and not have any "style" in terms of fonts and colors included. Would you want those to show as well?
Maybe send me a sample css style sheet and what you would expect to be the resulting styles list and I can try to figure out a way to add this feature in the future.
You could add styles to the .js file directly... you can read about adding styles from the ckeditor web site:
Styles
