Adobe Dreamweaver is the most popular WYSIWYG website creator. It has a built-in FTP client, handles linking between stylesheets, images and HTML pages, and has a host of other features. If you absolutely must use a WYSIWYG editor, and can afford (or already have) Adobe CS, check it out.
However, with any WYSIWYG HTML editor, you will run into eventual problems. Even when hand-crafting code, it is often difficult to achieve cross-browser compatibility; visual editors are even less precise. Sites created in WYSIWYG editors tend to be lower quality, not to mention a pain in the rear to update.
While I don't know the specifics of your situation, if possible, you might want to look into setting up some type of content management system where users could log in and make basic changes to their own portion of a site, while maintaining a consistent theme and having a more easily updatable system. Popular CMSs include WordPress, Drupal, SilverStripe and Joomla.
Depending on the complexity you need, you might even be able to get by with something as simple as one of the many online site building tools. Google Sites is one option; there are dozens more.