Hi – great question!
I have to stress first of all that in building on top of an ecommerce engine like WooCommerce we aim to actually interfere in its operation to the minimum extent possible.
What you’re describing really sounds like a facet of WooCommerce and I’d encourage you to approach them if you need further help here – but you may well be interested in this approach to automating completion of orders which originates in their documentation.
I hope that helps – and let me know if we can assist with anything else 🙂