I saw this thread Check user is in User Group / Custom User Permissions had an idea. Can I use USER group to limit who can see the Author dropdown on the entries form? Is this even permitted the craft license. I really need to remove that field from view of two user groups. Also would be nice to be able to limit which fields a user has access to when creating an entry.
You can use the Control Panel User Group plugin to automatically add special classes to the
<body> tag in the CP.
* Disclaimer: I'm the author of all of those plugins. :)