Custom Admin functions for Open Cart

I have attached a full brief in Word format which you will need to read, but I need some custom Admin functions implemented with VQMod. The store is being run via MijoShop plugin which is OpenCart inside Joomla. Curent OpenCart version is 1.5.51. Admin add a lot of orders by hand for their customers. The default Open Cart interface is not suitably set up to do this in bulk. They would like to create a new ordering screen along these lines (see image 1 below for extra details). • All products (approx. 400) are shown on one page but in tabs sorted by manufacturer i.e page is loaded once only to access all products • There are approximately 40 brands • Products can be added / deleted from cart without reload (AJAX) • Discount can be applied to each product by $ / % amount • If only Address is available under Payment details then it should autofill • If only Address is available under Shipping details then it should autofill • Ability to edit order information prior to final submission of order i.e summary screen after selecting all other options To summarise, they would like the possibility of ordering from the Admin interface in a substantially more efficient method than Open Cart offers. I am open to your suggestions on how you might go about implementing this. The deadline for this is 12th February.