ok
let me tell you i have recently implemented same things as you requested here.
In that application my client uploading product with the help of third party software. So i implemented the application which will upload the products to amazon store including product feeds, image feeds, inventory feeds, price feeds and variation feeds (parent > child ).
I have also automated the process and make it cron which will periodically fetch the inventory from the source file (form the distributor location - that is located on other server and i am communicating it with ftp api ) and update the it with existing products in the amazon store.
let's discuss in details with the project.
Looking forward for your response.