Amazon and Ebay reporting tool

Hi there, I am after building a detailed analytics reporting tool for our business. This is very extensive reporting that we need for our business as we sell things on Amazon, ebay, websites and other marketplaces and channels. We have sales coming from different accounts in US, Canada, UK, Europe, Malaysia in different currencies and we need to analyze them. In order to do this, we need to build our monthly profit and loss reports and that will include our sales, Cost of Goods, channel cost like Amazon, ebay fee, FBA cost, shipping cost and it all have to come direct from marketplace through webservices. So someone with strong experience of Amazon and ebay webservices would be able to retrieve information from our accounts and club them based on our desired groupings. We don't care what channel product is sold on. We only care about our own groupings as we group our various types of categories/products into different groupings and we want to know individual product profit margin, gross margin, category level margin, product level margin, daily margin, monthly margin and all those sorts of analytics once we have all the required data in our hand. Someone with solid experience in this kind of work would be desireable. We will build a detailed Scope of work. However with this nature of work, I am sure there would be tons of changes and we will rely on your experience, expertise and guideline because we may not be expert enough on what exactly we want to see and how the data and reports should be presented to us. So that is the reason we need help of good expert who knows what we may want to see and how it should be presented to us and help us building a detailed scope of work before we commence. Thanks Sunny