Woocommerce WP - make changes in custom plugin for subscribtions

Overview: You can purchase products yourself or by subscription plan. At the moment the subscription works in the following way: the user goes to the subscriptions page > chooses subscription > goes to the step where he/she can choose products > goes to checkout. SUBSCRIPTION PAGE: - list of available subscriptions: when the user clicks on the selected subscription, to class "as_subscription" should be added class "selected" and that's it, the user should not be redirected anywhere, the user should only select the option by clicking on it, - adding a calendar (can be by plugin), where the user will select on which day user wants to start the subscription - this calendar, however, will be adminable by the admin, which means that the admin will be able to define which days in the calendar are available to start subscription (for example, only on Mondays), - main button redirects user immediately to checkout, where he has to pay for subscription. When the user pays for the subscription, then will be able to see the subpage with the products in the subscription (in my account page). SUMMARY: in order to get to the checkout page, the user has to select the product and the subscription start date. SUBSCRIPTION PRODUCT PAGE: - after buying subscription user can choose products by going to my account > subscriptions > here should be list of bought subscriptions and after clicking on proper one user is redirected to this subpage with list of products, - if user doesn't choose the products in time (max 72h before shipping), admin should be able to define somewhere in the platform the set that will be sent (these will not be random products, it have to be products defined by admin), WP ADMIN: create a subscription plan: - adding products to the subscription by adding categories, - narrowing products by attributes - once all the products have been added, the admin would like to be able to easily exclude some product, Explanation: for example - there is a plan to subscribe 6x 900ml soups (only this capacity), the admin has to click as little as possible to add these products, so he first selects the category Soups, and then narrows the capacity to 900ml (attribute), or in reverse order. Then the admin says that one of the added 900ml soups is too expensive to be in the subscription, so he only wants to remove it, leaving the rest.