In my opinion and if I get your question right, there are several ways to solve this with standard Odoo, remember the possibilities with Odoo are endless depending on how you configure the system.

A solution would be to create 1 company with several warehouses (abroad) and only for the main warehouse (at head location) you will have the "multi step" delivery. This allows you to centrally purchase and receive the product and then redistribute them between your warehouses.

- 1 Central purchase location (only 1 company);

- Multi showrooms all over the country (multi warehouse);

- 4 Steps confirmation (change routing of warehouse in which you receive products);

- Maybe think or Resupply warehouse possibility.

This is just 1 solution, another possibility would be to directly deliver to each warehouse. This however means that you will have to create a separate purchase order for each warehouse.