Hey, great work on migrating stock to Drupal 8.
Had a look at the module (made a first pull request for a composer.json file) and like the way it works and fits in with the Commerce ecosystem I proposed last year.
Including all the UI actions and services adds a whole new level, but I think it would be better to separate these out.
If I already have an ERP system I only need all of the entity types for stock and the checkout type actions. All the management, stock receipts etc are managed in the ERP and synced by a REST API etc.
So the base functionality can be in the Commerce Stock module, and then the Commerce ERP module extends that with the UI for managing stock in Drupal.
There could then be integration modules like the https://www.drupal.org/project/commerce_unleashed to sync stock data and actions with and external ERP system.