change my bigcommerce site in magento

Migration from BigCommerce to Magento ver. 1.9.3 (Graphics from the existing site can be sent over as files sized to match the new template) At this point in time the install can be uninstalled and a different version of Magneto could be installed if necessary. (Default CPannel Install) Magento will be hosting multiple stores in the future (domain 1 & domain 2...etc.) from the ground up this needs to be set up correctly. (Strong and defined logic for what is global) RMA logic setup The business sells original products once that product sells we want a automatic redirect in place that would lead the user to the category the product was in. For example: [login to view URL] The above script would do the reverse if /ItemA has stock or quantity is not 0 NICE TO HAVE: Store exposed in Facebook, twitter & pintrest or posting ability. Google Shopping feed set up and tested All products can be sent over from existing site with a inventory management utility we use called ecomdash if appropriate. (The site you will be copying is live and new items are added daily and sell out daily) all product url's need to remain the same, we will simply re point the Name Servers to the new site. one page checkout if possible for clients Admin needs the ability to process a phone order and authorize a credit card over the phone NICE TO HAVE: Admin needs the ability to create a order for a customer, an e-mail is sent to the customer to complete the checkout 10 percent coupon offer when a new visitor browses site for the first time. Coupon use 1 time only per visitor. NICE TO HAVE POS Interface (Support for looking up items by our SKU's and UPC Codes) most products are bundled and include various accessories. If a customer is interested in a product the price is defaulted as a bundled purchase however they need the ability to swap out bundled accessories, (Other products in store bundled with product) which will change the price of the package. (Need a strong logic and ideal way to handle this)