I'm uncertain whether this will address your larger issue of what happens when
content is pasted, but you can limit users to using styles contained within a
CSS file. Here's how:
1. Do Edit | Administer Websites, and select the web site in question.
2. The Administer Website dialog appears. Under Users and Roles, select the
role you wish to tailor, and click Edit Role Settings.
3. On the dialog that then appears, under Styles and Fonts, you can uncheck
several items, and also set it up to allow styles from a specific CSS file if
Again, I'm not sure what this does for pasted content, as I've not tested that
personally, but hopefully the response is helpful.