It would be really nice to see virtual Card numbers or controlled payment numbers for the below use cases (there will be more I am sure) would be very handy. Mastercard already have this capability.
Card number for use with only one merchant, when leaving card details with the likes of Ticketmaster it would be super easy to track fraud back to the originating (breached) merchant/website.
Card number for one time use. When purchasing with a merchant who you cannot completely verify, or purchasing with high risk websites such as crypto currency exchanges.