Amazon, Ebay marketplace order, inventory synchronizaion

Project Description:
I have a B2B wholesale ecommerce website (php, mysql based, using cs-cart source code as a base). My website allows my merchant customers to buy their inventory in bulk for their online stores on amazon.com and ebay.com. Once the inventory order is placed from my website, the inventory will be prepared and sent to Amazon fulfillment center. My staff will also help my merchant customers to setup their product listing in their amazon.com and ebay stores. (This wholesale part of my website is being developed)
The goal here is to allow my customers to fulfill their orders on multiple channels with a synchronized inventory system. All inventories are physically stored in Amazon Fulfillment Center. By default, FBA (Fulfilled by Amazon) will automatically process all amazon.com orders for my merchant clients. FBA will also to process non-amazon order shipping if my merchant customers manually enter the order information ( customer name, and shipping destination etc.). I would like to have this step automatic. In this very first version, ebay is the only non-amazon.com sales channel I would like to implement for my merchant customers. (In the future version, I would also like to add support for other platforms such as buy.com, sears, shopify, etc. )

A very good working example is autoMCF.com. please create a trial account and study it in detail
http://automcf.com/how-it-works/

I need the exact same function as how the website process information. For every merchant customer, my program needs to
A. Connect Fulfillment by Amazon and marketplace accounts (ebay) onto my website
B. Inventory gets imported from Amazon, and my merchant customers decide which items his ebay store should manage/sale. Automatically setup store for his ebay accounts
C. Ebay orders are automatically retrieved and sent to Amazon (item SKUs will be the same across ebay and amazon inventory)
D. Amazon picks, packs and ships your multi-channel orders
E. Orders are marked as shipped and tracking numbers are added
F. Inventory quantities are updated across all marketplaces