WooCommerce Subscriptions

My client gives a trial period which must start from the day after the goods are shipped. The goods can take a variable period from the date of order to get ready to ship. If we could generate the trial period from the moment that the order is marked ‘completed’ it would be much simpler to manage. Currently they have to edit the trial end date, next payment due date and subscription ends date manually for every order when the goods are shipped.