Altough this plugin will eventually find its way into Core, for a period of time it will need to work alongside existing WooCommerce versions. WooCommerce requires WP 4.7 and PHP 5.2: https://github.com/woocommerce/woocommerce/blob/master/phpcs.xml#L18-L19 So, if we want to be inside of WC core, we'll need to match that. What versions of WooCommerce should we support? Should we aim for just 3.6+, since that version will be already X months old when we release WooPay?