Wordpress Theme Customisation

Take an established Wordpress Directory theme (Wyzi: [login to view URL]), and modify to allow multiple subscriptions that are tied to each individual listing. Currently the theme's subscription model (using Paid Membership Pro) is user based, not listing/business based. Likely will need to integrate WooCommerce Subscriptions to allow this, and so a business owner can create as many listings as they want - and for each one choose the subscription package (either free or paid). Currently on the user dashboard, all the listings are displayed - and they can edit each one. With the new modified theme, each listing should also show which subscription level it is currently on. The user (business owner) will then be able to upgrade/downgrade any listing whenever they want. To summarise the end requirements: - User (Business Owners) only need to have one account - User can add as many businesses to their account as they want - User can decide for each business if it will have free/pro features - this can be upgrade/downgrade at any time - Each pro business added to their account creates a new individual subscription charge (separate recurring date). - Only will be two package types (free or pro) Any customisation will need to be done in a way that will allow future theme updates without overriding these modifications. Most of their current functionality is inside their own plugin, so perhaps some sort of Child plugin (if possible) is needed, along with Child theme.