Customized Punchout Webshop Application

Custom eProcurement online application that uses the Punchout technique. The site needs to be able to communicate with ERP software like SAP, Ariba, etc. You need to make a very user friendly dashboard which contains: - customisable order forms which create a shopping cart item; - shopping cart interface; - order overview; - administrator interface, to easily connect and disconnect customers (and later suppliers), create new order forms, etc; - electronic invoicing; Please advice in expected hours, used skills, etc.