Does this exist????

I'm looking for a PHP based website management system. There are quite a few really good ones posted on sourceforge, but what I'm looking for is a little bit different. Things like polls and wikis are of no interest to me. I need a system that is dynamic in design/layout. It's to create business websites. The idea is that users who have little/no web knowledge and do things like change menu items, create pages, change banners and what not. They would need to be able to actually change the layout through a web based interface. I like the interface used in phpwebsite for creating pages, but it seems limited. I need users to be able to upload images that pertain to a page/article and be able to position those images wherever they want. I want to be able to predefine templates whose content is database driven and the users can map these templates/pages to navigation items dynamically. The more that I think about it, the harder it is to describe what I'm looking for. But I'm hopping someone has an idea of what I'm talking about. I'm prepared to get a team together and begin development of such an application, but I figure if someone else has started it, my efforts would be better used supporting their groundwork. After all, isn't that what open source is all about :) - Anthony