If you can code, it should be possible. In my oppinion in the A5_ExcerptClass there's a possibilty to add a class to the readmore link.
Then in the CC_WidgetClass you have to change some lines of code to give that class (that you ideally created in a css file) as a parameter to create the excerpt.
If wanting to be more comfortable, you even could add an input field to the widget controls to enter a class name which would be taken as that parameter for the excerpt.
That's in short, how you can fix it the 'dirty way'. Problem is of course that you will lose all your changes with an update of the plugin.