One thing that would be helpful for you as you work through design issues, for users of your software trying to decide if it supports their needs, and for others wishing to help is a definition of what constitutes "content" within your CMS. Is content only HTML files or can it include other text files? What about binary files, like pictures that may be attached to articles? Knowing what content needs to be supported will help to define requirements.

I am not sure what the "website as-is" in the requirements means. Is the intent to manage all files related to the website, scripts and all, or just the data that is displayed?