[vbboarder]

Cool idea, would be a great mod when you release it.

Have you tried using some JS, like find:

onclick="return false"

Replace with:

onclick="this.className = 'buttons'; return false;"

.
Maybe the class name is not registering when the multiquote state changes. If that doesn't work, maybe you can try similar onclick code with your previous case where you were using 2 css classes. For example, find:

onclick="return false"

Replace with:

onclick="this.className = (this.className == 'buttons1' ? 'buttons2' : 'buttons1'); return false;"

.
Hope that helps, good luck