I hadn't seen CushyCMS. Just checked it out. The way it works seems entirely different from what I'm talking about. I want to be able to add a page designer to my site for my many thousands (or millions) of users. Or whatever I want. CushyCMS wants FTP/SFTP information for single site and it's not at all clear whether I can integrate it into my own site.
Oh I see what you mean. Then you want eXponent CMS. www.exponentcms.com. I'm good friends with the people who developed it, and I've used it myself it's a great package.
Lets you edit pages with a WYSIWYG interface instead of plugging in code or dealing with text templates. Give it a shot.