Multi-Store Re-platforming with Marketplace Integrations

We are looking for a partner to advise us and work with our team to accomplish the transition to a new platform. The primary goal is to have a manageable system that integrates all aspects of our business. The ideal partner would have knowledge and experience in deploying multi-store ecommerce platforms that integrate with marketplaces (Amazon, eBay, Walmart, Etc.) Please see attached, detailed RFP.