CSS switching only works if you send all content to the user regardless of the role, then just "hide" it with CSS. That's completely insecure, obviously, and not how Plone works. To see something from the perspective of another role you'd have to login as a user with that role. Anything else would intrinsically require a complete bypass of the security constraints and open your system to hacking. Which may be an option for other systems, but not for Plone.