Customization to WooCommerce Subscription plugin

My e-commerce will sell subscriptions by using WooCommerce and WooCommerce Subscription plugin. I need a couple of features: 1) the cart icon should display the overall cost of the items already in the cart (now it shows only the number of items in the cart 2) a feature that allow customers that already have a subscription to add new items to this subscription instead of creating a new subscription. This should be done: 2.a) by adding a button to the shop page when the customer is already logged in and owns already a subscription in status active or suspended. In this case, even if products added to the existing subscription has a subscription fee, this is ignored and only recurring fee should be included in the order 2.b) by adding a button to my Account page under each subscription if the customer owns already a subscription in status active or suspended. If the customer clicks on this button he will be redirected to the shop page and all the products in the cart will be added to the already existing subscription. Also in this case, even if products added to the existing subscription has a subscription fee, this is ignored and only recurring fee should be included in the order. In this case products that are already in the active subscription should not be displayed in the shop page