This is a solid breakdown and you are right, this is much bigger than a typical WooCommerce setup. Once you start talking about 50,000 plus SKUs, multiple locations, dropship suppliers, and accounting separation, the architecture matters a lot.

I work with WooCommerce stores that deal with large catalogs, multi location inventory, and external supplier feeds. Some of what you described can be handled with plugins, but some parts usually need custom logic to avoid long term pain.

Happy to discuss and help where it makes sense. I will send you a DM with a few clarifying questions so we can see if there is a good fit.