> Also, it must be ensured that user data is accessible to all competitors.
This doesn't sound like a good idea. The collection of user data and the underlying advertising business model is a problem to be removed, not a playing field for more competition and "improvement".
The only way to make it inaccessible to competitors is to make it impractical to access for the user themselves. GDPR demands this portability and in theory, it's awesome. Though I haven't seen a lot of examples yet it should make it easy to do things like port your favourites and listening history from spotify to another platform. It's your data, after all.
This doesn't sound like a good idea. The collection of user data and the underlying advertising business model is a problem to be removed, not a playing field for more competition and "improvement".