Irrespective if the users belong to the same paying package, the ability to share data/links from one ProtonDrive to another ProtonDrive either by allowing shared link to be directly accessible or other means to achieve the following:

1. User A upload to their ProtonDrive
2. User A share a link to User B
3. User B access the link
4. User B download locally link content
5. User B upload content in their ProtonDrive

make 3. and 4. and 5. be directly in ProtonAG servers.