Hi,

It sounds like you're on the right track with your eCommerce network setup! Since you're looking to build an MVP web app that includes order management, purchasing, invoicing, supplier management, and inventory, there are a few open-source solutions that can serve as a foundation for your project. You could consider frameworks like Laravel or Django, which provide strong back-end structures and are easier to work with than PHP if you're looking to move away from it. Both frameworks also offer excellent community support and scalability.

Additionally, you can integrate your custom features by using APIs, like the WooCommerce API, to manage products and orders while leveraging tools for invoicing and inventory. For a more comprehensive solution tailored to your needs, you might find inspiration in a custom order management system that could be adjusted to suit your business model: https://www.cleveroad.com/blog/custom-order-management-software/

Hope this helps!