CMS needed

I need a CMS created for a website with several million pages. Most of the pages are nearly identical, and I would like to be able to add and remove video, text, scripts, code, and images to all of the pages, or just some of them, very easily. My pages are getting de-listed from Google because they are too similar, so my goal is to be able to vary the content to them via a CMS. A basic understanding of SEO and the ability to come up with additional solutions for my duplicate content issues would be beneficial.