Build a Website builder - Drag & Drop, inline editable

Looking for a website builder which can be used by users to create their website using ready to use templates provided by us. the site needs : - to be very easy to use (drag and drop) - few design templates - be able to interact with the already existing code of the mother site - option to add pages , moves pages as main page, sub page. - inline editor for live editing of text, change color, change banners - have advanced SEO section - option shopping cart