Create an e-commerce using an open source platform (WooCommerce, Open Cart, Zen Cart)

I need to create an e-commerce using an open source platform like: WooCommerce, OpenCart, ZenCart, etc. I have experience with Shopify, but in this case I need something simpler to save the monthly charge and transaction fees. I want to sell woman shoes in México through this platform and all of my clients are wholesalers. At this moment I am not really interested in selling shoes to the end-user but it would be nice if the platform is ready to sell both type of customers. Besides the basic features that require an e-commerce platform (management of orders, products, collections, customers, discounts, reports, creation of pages, payment methods, email notifications) these are some special requirements for this project: - A product administrator capable to add many variants to the products (size, color, material, etc.) - Order manager, capable of shipping one order in partial shipments and send email notifications to the customer regarding to his order status - Capable of add custom payment methods - (Preferred) Capable of get integrated with a local payment methods in Mexico like: DineroMail / Conekta / MercadoPago - Capable of add a bluk discount plugin, for example: add a variation to the price according to the number of units you sell Once created the cart, we would need to be instructed in the usage of chosen platform to be able to manage it.