An MVP of the feature plugin (for eventual proposal for inclusion in WordPress core) could:
add a means to the User Profile page by which a user or an admin could download the user's data by aggregating the responses from each activated plugin that implements the GdprInterface interface
add an action to the User Profile page and/or Users (List) page by which an admin could anonymize and/or delete the user's data, including calls to each activated plugin that implements the GdprInterface interface
add a means, possibly to Settings > Reading, to set the what page the Privacy Policy can be found on
add shortcode(s) (useful when editing that page) that return the privacy policy section(s) returned from each activated plugin that implements the GdprInterface interface
provide us a "playground" to test everything as we develop the GdprInterface interface and add it to plugins
Beyond MVP, we could look at things like
hooking calls to delete_userdata on each activated plugin that implements the GdprInterface interface as part of the delete user action
adding REST API interfaces for reading, deleting, anonymizing user data
adding REST API interfaces for plugin privacy policy text
creating Gutenberg blocks to aid in privacy policy assembly from the installed GdprInterface implementing plugins
An MVP of the feature plugin (for eventual proposal for inclusion in WordPress core) could:
Beyond MVP, we could look at things like