I am expert in amazon MWS API, I have used all libraries under amazon MWS e.g. feed submission, product, order, fulfillment etc etc.
I have rewritten MWS src to make it multicurl suitable so that we can send multiple calls at once.
you can see my profile feedback, I have completed more than 15 projects based on MWS only e.g. amazon repricer, amazon order management, creating amazon new products. I can easily integrate any app into Magento
Message me for more details and discussion.