Drag and Drop Website Builder

I will be creating an online portal via Joomla; members of this portal must have the ability to create their own websites via a web site builder. This builder must be drag and drop as I have to take into consideration that the member has no skill in web design or development. If the builder being used is from an open source software that is already available on the market, that is fine, however, it must be able to share or bridge to the master Joomla database of the portal. I will be providing the templates. The builder should facilitate normal features such as adding images, background colour changer,content, static pages, form builder, image and video gallery. It must be so simple an 8 year old can create a site within a matter of minutes. Since the member may not have any image editing software, they should be able to upload any image within the specific area of the template and it would re-size to the dimensions of that space on the fly. I will be using php/mysql. There must be a solid reporting feature in the back end as well, which shows the basic data as in any web trend. Please show me some past examples of your work of anything related or close to something like this