Could you use PHP to "build" a CSS stylesheet on the fly?
What I was envisioning - forgetting fast - is an ability to be able to click check boxes or radio buttons in a control panel and then have it change the style of elements.
Not the same as having 3 stylesheets on hand, mind you, but a way to tweak things more.
Say I want to change all control from white to light blue, and make my background dark blue from white, and my text from black to white. I could click those element boxes and voilà, things change.
Next maybe I'd make the control yellow, text red, and leave the background white.
I just think that would be a good way to do a "website color scheme picker" as well as show people the power of CSS!