Develop a Plugin for 2 way API Integration between different ecommerce platform sites

Want to develop an 2 way API integration ready plugin for our Wordpress ecommerce marketplace (Theme-Marketica) where, - our vendors will upload their products from their individual frontend accounts - our another group of re-sellers (other than vendors) will visualise the uploaded products in catalog form without checkout button. They will shortlist the products and add their margins and shipping charges to this list of selected products and based on API integration to their ecommerce site, these products will be auto-uploaded on their server and the products will be made live instantly. -After generating orders on their individual sites they will import orders in our marketplace website (through API) which will be fulfilled by us in exchange of certain fulfilment and shipping fees. - Thus all our resellers might be having different ecommerce websites but they should be able to upload product feed through API and export the orders through API with click of a button. Any information required will be entailed further only to interested freelancers.