What we are trying to achieve is a seamless integration with order/transaction data that has come from a legacy system, and without turning them into actual WooCommerce orders and inserting them into WooCommerce (theres 800k so far..).
When a customer is looking through their list of orders, they shouldn't see a different in the look of the non-WooCommerce (pre-WooCommerce) orders and WooCommerce orders (which are just posts within the system).
We want this data stored separately for various reasons, i.e. tables storing the historical data.
We're currently modifying any actions that interact with the order but are looking for a cleaner solution that would focus on extending the WC_Abstract_Order or WC_Order, has anyone dealt with this before?