Hi, I can implement this for you, I have experience integrating many payment gateways in many shopping carts, including Woocommerce, Magento, OpenCart, Prestashop etc.
I checked both documents and I'm confident I can do it, unfortunately I can't code a prove of the CUSIN generator/sender because it will take me time and is almost the core of the plugin and I'm not guaranted the award of the project unless you pay for it.
I'll code a standard WP plugin/Woocommerce payment gateway following all the guidelines, nothing hardcoded.
It might take me up to 20 days.
If you have any question just let me know.
Greetings!